Global Solar Technology—South East Asia [spring 2010] by Trafalgar Publications

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Southeast Asia

News for the Solar Manufacturing Industry

Covering India, Thailand, Malaysia, Singapore, The Philippines and Hong Kong Volume 1 Number 1 Spring 2010

Transfer Transfer printing: printing: an an emerging emerging technology technology for for massively massively parallel parallel assembly assembly Converting Converting considerations considerations for for flexible flexible materials materials Materials Materials and and the the growth growth of of PV PV technology technology

K Subramanya Column Inside NEW PRODUCTS INDUSTRY NEWS INTERNATIONAL DIARY

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Contents

Southeast Asia

Covering India, Thailand, Malaysia, Singapore, The Philippines and Hong Kong

Global Solar Technology is distributed by controlled circulation to qualified personnel. For all others, subscriptions are available at a cost of £110/US $220/€165 for the current volume (6 issues). No part of this publication may be reproduced, stored in a retrieval system, transmitted in any form or by any means—electronic, mechanical, photocopying, recording or otherwise— without the prior written consent of the publisher. No responsibility is accepted for the accuracy of information contained in the text, illustrations or advertisements. The opinions expressed in the articles are not necessarily those of the editors or publisher. © Trafalgar Publications Ltd. Designed and Published by Trafalgar Publications, Bournemouth, United Kingdom www.globalsolartechnology.com Gloabl Solar Technology Southeast Asia Volume 1 Number 1

Southeast Asia

News for the Solar Manufacturing Industry

Covering India, Thailand, Malaysia, Singapore, The Philippines and Hong Kong Volume 1 Number 1 Spring 2010

Contents 2

Volume 1, Number 1 Spring 2010

Welcome Trevor Galbraith and Debasish P. Choudhury

Technology Focus

Transfer printing: an emerging technology for massively parallel assembly C. A. Bower, E. Menard, P. E. Garrou, Semprius, Inc.

12 Converting considerations for flexible materials Josh Chernin, Web Industries 16 Materials and the growth of PV technology David A. Preische, Indium Corporation of America

20 Atmospheric plasma surface modification for continuous processing of solar cells Rory A. Wolf, Enercon Industries Corporation 24 Combating the impact of contamination in solar cell production Sheila Hamilton, Teknek Special Features

18 26 30 36 40

Interview—Paul van der Wansem, BTU International Light of the world: Building success as the solar industry goes global Interview—Paul Davis, SEMI Solar PV systems market in Southeast Asia to reach US $255 million by 2016 The billion dollar question, a special column by Mr K Subramanya

Regular Features

4 32 34 38

Industry News Technological developments New Products International Diary

Solar Solar cellS cellS on on ultra-thin ultra-thin cryStalline cryStalline Silicon Silicon Solar Solar cell cell proceSS proceSS temperature temperature meaSurementS meaSurementS Spring 2010

Steamer Steamer vS. vS. torch torch in in pv pv manufacturing—a manufacturing—a coSt coSt of of ownerShip ownerShip compariSon compariSon

NEW PRODUCTS INDUSTRY NEWS INTERNATIONAL DIARY

Welcome to the premiere issue of Global Solar Technology—South East Asia.

Visit the website for more news & content: www.globalsolartechnology.com.

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Global Solar Technology South East Asia – Spring 2010 – 1

Editorial

Trevor Galbraith

Editorial Offices

Europe Global Solar Technology Trafalgar Publications Ltd 8 Talbot Hill Road Bournemouth Dorset BH9 2JT United Kingdom Tel: +44 (1202) 388997 news@globalsolartechnology.com www.globalsolartechnology.com United States Global Solar Technology PO Box 7579 Naples, FL 34102 USA Tel: (239) 567-9736 news@globalsolartechnology.com China Global Solar Technology Electronics Second Research Institute No.159, Hepin South Road Taiyuan City, PO Box 115, Shanxi, Province 030024, China Tel: +86 (351) 652 3813 Editor-in-Chief—Trevor Galbraith Tel: +44 (0)20 8123 6704 (Europe) Tel: +1 239 567 9736 (US) editor@globalsolartechnology.com Managing Editor—Heather Lackey hglackey@globalsolartechnology.com Editor—Debasish P. Choudhury dchoudhury@globalsolartechnology.com Circulation and Subscriptions Tel: +1 (239) 567 9736 subscriptions@globalsolartechnology.com

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Editor in Chief

Welcome! It gives me great pleasure to welcome you to our first edition of Global Solar Technology—South East Asia. Global Solar Technology has a global reputation for providing solution-led technical articles and factual business content that keep engineers and scientists up to date with the latest developments in solar manufacturing. Global Solar Technology—South East Asia covers India, Thailand, Malaysia, Singapore, The Philippines and Hong Kong. The focus will be to bring you local news, columnists and information,

reinforced by international technical articles, business trends and new products. We hope you enjoy this issue and look forward to hearing your views. Trevor Galbraith Publisher and Editor-in-Chief Global SMT & Packaging

From the editor.... I am absolutely delighted to present the inaugural South East Asia edition of the Global Solar Technology magazine, on the historic 10th anniversary of our company. It is a momentous occasion for all of us at Trafalgar Publications Limited to launch the first regional edition of our international publication, Global Solar Technology. Since, its formal launch at 23rd EU PVSEC 2008 show in Valencia, the magazine shot to fame as the leading authoritative technical magazine for the solar manufacturing industry in a very short span. Let’s talk about the industry now! Solar power is a heavyweight in the renewable energy category and is growing at 40% annually. There is no doubt; Asia is playing a key role in the development of the global solar energy industry. The prominent contributors are China, Taiwan and Singapore. India has vast solar energy potential, which is currently underutilized. However, the strong government support for solar energy came through the announcement of National Solar

2 – Global Solar Technology South East Asia – Spring 2010

Mission late last year, setting the target of generating 20 GW of solar power by 2022, has put solar on the solar industry on the growth path. Still, the high cost of solar cells remains a barrier in the development of solar energy market in Southeast Asia. The Solar Energy Research Institute of Singapore SERIS under the leadership of Prof. Joachim Luther, who is a former Director of Fraunhofer ISE of Germany, is carrying out research in the areas of solar cells and module development. However, the leading Asian companies too should concentrate on research and development to develop low cost substitutes to silicon with similar conversion efficiency for large-scale deployment of solar energy in the region. —Debasish P. Choudhury Editor Global Solar Technology South East Asia

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Industry news Title

Industry news Fraunhofer ISE and VDE of Singapore expand cooperation In cooperation with the Solar Energy Research Institute of Singapore SERIS, the VDE Institute and the Fraunhofer Institute for Solar Energy Systems ISE have opened the first testing and certification center for photovoltaic modules in South East Asia, located in Singapore. The new joint venture company VDE-ISE Pte. Ltd., founded by VDE and Fraunhofer ISE, is under the leadership of Henry Paetz. The company is responsible for the customer service, certification and safety tests according to IEC 61730, while the Solar Energy Research Institute of Singapore SERIS under the leadership of Prof. Joachim Luther carries out the various performance tests. www.ise.fraunhofer.de India solar PV market shines bright as the government encourages private investments The Indian solar PV market has come of age in the last two to three years, with the market growing from a ten-member sector to a well-organized market with more than 30 world-class PV module and cell suppliers. The aggregate module production capacity rose from less than 60 MW in 2005 to more than 1 GW in 2009, setting India up as a possible major manufacturing hub for the global solar PV market. New analysis from Frost & Sullivan, :India Solar Photovoltaic Market,” finds that the aggregate module production capacity in the market was 972 MW in 2008 and estimates this to reach 2,575 MW in 2015. The market can look forward to large-scale private investments across the PV value chain, especially in the production of polysilcion feedstock, silicon wafers, PV modules and cells, as well as balance of system components. “Successive reforms in the power sector and a plethora of policies initiated at the central and state level to control green house gas emissions and promote renewable energy has restored investor interest in the solar power industry,” says Frost & Sullivan industry analyst Hemanth Nayak. “Several private firms are expected to make large investments to avail financial incentives and leverage the cost advantages of solar PV production in India.” www.energy.frost.com

The Norwegian Prime Minister visits Scatec Solar’s rural electrification project in Rampura, UP The Norwegian Prime Minister, Mr. Jens Stoltenberg, made a visit to Rampura in Uttar Pradesh, the first village to get a Community Solar Power Plant by Scatec Solar on Feb. 5, 2010. The visit comes as the company, together with Indian and Norwegian governments, is about to launch the scaling-up of the solar energy project for rural electrification in India. Indian and Norwegian governments in partnership with Scatec Solar will jointly finance the expansion from two to 32 villages, impacting approximately 1800 families. www.scatec.no

Linde Gases Division of The Linde Group closed 2009 with more than 6 GWp of production capacity across its global photovoltaic customer base. Linde demonstrated increased market traction securing multiple new contract wins and renewals with leading thin-film and crystalline manufacturers worldwide including GS Solar and Suntech in China, Euro Multivision, Indo Solar and Solar Semiconductor in India, and Bosch, Malibu and Masdar in Germany. www.linde.com Berjaya Solar Sdn Bhd to develop Malaysia’s first large scale solar PV power plant Berjaya Solar Sdn Bhd, a wholly-owned subsidiary of Berjaya Corporation Berhad, announced the proposed development of the country’s first large-scale 10 MW ground-based solar photovoltaic (PV) power plant at Bukit Tagar, Selangor, estimated to cost approximately RM180 million. This is the precursor to developing a proposed 50 MW solar PV power plant in the future based on the success of the 10 MW plant undertaking. www.berjaya.com

Taiwan photovoltaic industry heading for growth in 2010 Taiwan photovoltaic industry revenue faces recession through upstream to downstream in 2009 due to the influence of global economic downturn, says PIDA. The total revenue shrinks to NTD 86.9 billion in 2009 with negative growth rate at 18% comparing with that in 2008. The majority of revenue comes from midstream waferbased and thin-film solar cells, which take approximately 70% revenue share of the UK and India launch GBP10 million industry by NTD 60.7 billion. Among all, collaboration on solar energy wafer-based solar cell manufacturing brings program a production value of NTD 59.3 billion. UK Minister for Business, Innovation and Upstream silicon ingot & wafer and Skills Pat McFadden and Indian Minister mid-to-downstream module and system for Science and Technology Prithviraj installation take only 26% and 2% share Chavan announced the new collaboration of the total revenue respectively. Upstream while chairing the bilateral India-UK silicon ingot & wafer though represents Science and Innovation Council in New a decline of revenue still reaches NTD 23 Delhi. Research Councils UK (RCUK) billion. In 2010, since the economy began and the Indian Department of Science and recovery, photovoltaic industry is estimated Technology (DST) have each committed to have an over 23% growth to reach NTD up to GBP5 million each over a three-year 110 billion. period for two research projects: As for now, most PV companies in • Advancing the efficiency and production Taiwan gather in Hsin-Chu Science Park of excitonic solar cells: focusing on the (HSP) and Southern Taiwan Science Park development of materials, structures, (STSP). Companies in these two science processing and photovoltaic panel parks contribute more than 60% of the engineering of excitonic solar cells - a class total production value in Taiwan. of non-conventional solar cell based on www.pida.org.tw new types of materials. It will build on existing research in both the UK and India Linde achieves growth, invests in to develop cheaper and higher volume innovation despite over-capacity in solar cell manufacture. RCUK and DST PV industry have awarded GBP2.5 million each for this Defying the impact of a depressed project economy on market movements, the

4 – Global Solar Technology South East Asia – Spring 2010

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Industry news

• Stability and performance of photovoltaics: focusing on improving materials supply and developing better designs to ultimately create cheaper and more efficient devices than current solar cells. RCUK and DST have awarded GBP2.4 million each for this project. The solar energy projects form part of the RCUK Energy Programme led by the Engineering and Physical Sciences Research Council. Aries Ingeniería y Sistemas commissioned for feasibility studies to develop two 50 MW CSP plants in India Aries Ingeniería y Sistemas has been commissioned from two relevant Indian developers to conduct the feasibility analysis to build two 50 MW concentrated solar power plants (CSP) in India. Both projects coincide with the favorable regulatory framework for renewable energy included in the National Solar Mission approved by the Indian government, which set a target up to 22,000 MW of installed capacity for the next seven years. In fact, Aries is putting its efforts into the research and evaluation of local manufacturers to bring down the cost of a CSP plant in India. Feasibility studies conducted by Aries Ingeniería y Sistemas will include the evaluation of the physical characteristics of the site and infrastructures required for this type of projects in accordance with the environment information, geographical, geological studies and all applicable existing regulations. Aries Ingeniería y Sistemas will also perform the verification of regulations and environmental conditions for both projects. www.ariespowerindustrial.com TSMC may set up thin-film PV plant at CTSP Taiwan Semiconductor Manufacturing Company (TSMC) may establish a photovoltaic (PV) production base on an 18-hectare site in the Central Taiwan Science Park (CTSP) to produce thinfilm PV modules, according to industry sources. TSMC is recruiting experts and engineers for PV business under its New Business Division, with the number of staff expected to reach about 100 at the end of 2009, the sources indicated. TSMC filed an application with the CTSP administration for renting the land to house a 12-inch fab at an estimated investment of NT$240 billion (US$73 billion) a few years ago, but in February

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2009 it gave up the application. However, TSMC has resumed the application specifically for the PV business project. Source: Digitimes, Taiwan. Greentech investment climate showing strong signs of recovery Venture Capital investment in greentech looked a lot healthier in the third quarter of 2009 compared to the previous two quarters of this year, according to a report by Greentech Media. The third quarter closed with US $1.9 billion invested in 112 deals compared to $1.2 billion invested in 85 deals in Q2 and $836 million invested in 59 deals in Q1. The dominant investment sector was solar with $576 million invested in 29 deals. Following solar was biofuels with $513 million invested in 17 deals and smart grid with $160 million invested in 14 deals. The year to date the total venture capital investment in greentech stands at $3.9 billion and is already the second best year for greentech. www.greentechmedia.com Q-Cells selects Camstar for new Malaysian mega-factory and upgrade of German production lines Camstar Systems, Inc., announced today that Q-Cells SE, the world’s largest solar cell manufacturer, has selected Camstar’s SolarSuite™, configured for the solar industry on the Camstar Enterprise Platform, to drive down cost per watt through improved process quality and cell efficiency. Q-Cells will deploy the solution in two new production lines in BitterfeldThalheim, Germany, and in its new factory in Malaysia, where production will exceed 300MW (peak) by the end of 2010. Q-Cells selected SolarSuite over competing options for its strong “out-of-the-box” functionality that is designed specifically for and widely used by Camstar’s global customers in the Solar and Semiconductor industries. www.q-cells.com, www.camstar.com Research and Markets adds Photovoltaic Technologies Equipment and Materials 2009 report Research and Markets announced the addition of the “Photovoltaic Technologies Equipment and Materials 2009” report to their offering. According to the report from Yole Développement, until the end of 2009 and during 2010, because of strong overcapacities, total revenue is forecast to decrease by 45% compared to 2008 to 1.5 Billion euro. Market demand is forecast to come back after 2010 and will progressively impact the production sites by increasing

the fab utilization rates. Investments in fab extensions and related equipment are expected to follow in 2011 although they will arrive with a slight time lag behind the demand increase. www.researchandmarkets.com Heraeus acquires LORD cermet thick film product line Heraeus has acquired the thick film cermet product line from LORD Corporation. LORD entered this market in 2002 by acquiring Metech, a manufacturer of cermet and polymeric thick film solutions. The Heraeus acquisition sees the transfer of cermet thick film technology, products and customers from LORD Corporation in Elverson, PA, to Heraeus Materials Technology LLC in Conshohocken, PA. The move reflects an ongoing Heraeus strategy to add customer value from a market leading position and further emphasizes long-term commitment to the thick film business. LORD Corporation will retain its polymeric thick film product line. www.heraeus.com Despatch Industries receives order for multiple UltraFlex firing furnace units from China Despatch Industries has sold multiple single and dual lane UltraFlex™ dryer and firing furnaces to a top Chinese solar cell manufacturer. The units were purchased to facilitate a major production expansion by the manufacturer. This is the company’s first UltraFlex dual lane sale to China. Despatch Industries currently holds the number one market share for metallization firing furnaces, having sold over 200 units into China alone, and has shipped over 10GW of firing furnace production capacity worldwide. www.despatch.com Thin-film technology’s share of solar panel market to double by 2013, says iSuppli Thin-film solar cells are rapidly taking market share away from the established crystalline technology, with their portion of photovoltaic (PV) wattage more than doubling by 2013, according to iSuppli Corp. Thin-film will grow to account for 31 percent of the global solar panel market in terms of watts by 2013, up from 14 percent in 2008. www.isuppli.com

Global Solar Technology – February 2010 – 5

Transfer printing: an emerging technology for massively parallel assembly

Transfer printing: an emerging technology for massively parallel assembly by C. A. Bower, E. Menard, P. E. Garrou, Semprius, Inc., Research Triangle Park, NC, USA Transfer printing is a newly developed process that enables the massively parallel assembly of high performance semiconductor devices onto virtually any substrate material, including glass, plastics, metals or other semiconductors. This semiconductor transfer printing technology relies on the use of a microstructured elastomeric stamp to selectively pick up devices from a source wafer and then print the devices onto the target substrate. The key enabling technique is the ability to tune the adhesion between the elastomeric stamp and the semiconductor devices. The transfer process is massively parallel as the stamps are designed to transfer hundreds to thousands of discrete devices in a single pick-up and print operation. Studies of the process yield indicate that print yields in excess of 99.9% can be achieved. In addition, experiments show that the chips can be printed with placement accuracies better than ± 4 µm @ 3σ.

Surface mount technologies, such as pickand-place assembly, are well established and used in the packaging of many microelectronic devices. Standard assembly equipment is also being used to pick-and-place small high-efficiency compound semiconductor solar cells in the concentrated photovoltaics (CPV) industry. Regardless of this ubiquity, serial pick-and-place technology is not well suited for a number of applications that call for large assemblies of sparsely populated, precisely positioned microscale devices1. Current assembly technology also places constraints on the numbers and sizes of solar cells that can be economically handled. Standard pick-and-place tools using vacuum collets are not well suited for handling devices smaller than 100µm2 or devices thinner than ~20 µm. Modern pick-andplace tools operate at very high speeds to achieve reasonable process throughput (> 1a

10,000 placements per hour), but this comes at the expense of placement accuracy. Even while operating at slow speeds, many pickand-place processes do not achieve placement accuracies better than +/- 20 μm. There have been several efforts to advance fluidic self-assembly approaches3,4 as potential routes to low cost parallel assembly of small devices. However, to date these efforts have not produced a technology platform capable of competing with traditional pick-and-place technology. Transfer printing using an elastomeric stamp has the potential to deliver higher throughput (parallel vs. serial assembly), better placement accuracy and easier handling of microscale devices compared to standard pick-and-place with vacuum collets. Transfer printing is essentially a massively parallel variant of traditional surface mount assembly and therefore is considerably less disruptive compared to fluidic self-assembly. 1c

Figure 1a. The transfer stamp is aligned to the source wafer. The stamp is moved down into contact with the released devices. The tethers holding the devices in place are not shown in this drawing.

Figure 1c. The transfer stamp is aligned to the target substrate and moved into contact with the surface.

Figure 1b. The transfer stamp is lifted away from the surface and the stamp posts are now populated with devices.

Figure 1d. The devices are transferred to the target substrate as the transfer stamp is moved away from the surface.

Keywords: Transfer Printing, Concentrated Photovoltaics, Semiconductor Solar Cells

This paper was originally presented at SMTAI 2008.

6 – Global Solar Technology South East Asia – Spring 2010

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Transfer printing: an emerging technology for massively parallel assembly

The transfer printing process was first developed in Professor John Rogers’ group at the University of Illinois. Examples of transfer printed semiconductor devices previously fabricated include high mobility silicon thin film transistors (TFTs)5-8, GaAs metal-semiconductor field-effect transistors (MESFETS)9,10 and GaN high electron mobility transistors (HEMTs)11. Recently, Ahn et al. demonstrated prototype 3-D heterogeneous circuits fabricated by transfer printing7. Semprius, a spin-out from the University of Illinois, is working to scale-up and commercialize this newly invented transfer printing technology. The devices to be transfer printed must first go through a process to delineate and release them from their source wafer. This method utilizes sacrificial release layers underneath the device layer. In the case of silicon devices, silicon-on-insulator (SOI) wafers represent a convenient and readily available source wafer5. For SOI, the silicon device is delineated by etching through the device silicon layer down to the buried oxide layer and then removing the buried oxide layer using a selective wet etchant. The devices are held in place using tethers microfabricated in the device layer. The tethers are designed to break or cleave in a controlled manner during transfer printing12. Similar sacrificial release strategies have been developed for many other device materials, including gallium arsenide (GaAs)7,9,10 and gallium nitride (GaN)7,11. Figure 1 is a schematic illustration of the transfer printing process. First (Figure 1a), the transfer stamp is positioned over and aligned with the source wafer. This is accomplished using the custom transfer printer shown in Figure 2. The printer, which consists of a 6-axis (x, y, z, θz, pitch, roll) motion platform, allows for the transfer stamp to be moved relative to the source and target substrates. In addition, there is a camera positioned above the transfer stamp that independently moves (x, y, z) relative to the stamp. The transfer stamp is transparent and the camera looks through the stamp to align the stamp relative 1e

Figure 1e. The transfer stamp returns to the source wafer and steps over to the next set of devices.

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to the source wafer. An image of the transfer stamp is shown in Figure 3. The inset shows a scanning electron micrograph of the stamp surface (the stamp was coated with Au to prevent charging). The elastomeric transfer stamp is fabricated using previously described molding processes13. In brief, an inverse of the desired stamp pattern is generated using a photodefined polymer master substrate. The elastomer (PDMS) is cast against the master substrate, cured, and then delaminated to form the stamp. The master substrate can be reused to generate additional transfer stamps. After the stamp is aligned and brought into contact with the released devices, the stamp is lifted away from the source

Figure 2. Semprius transfer printing tool.

Figure 3. Transfer stamp and scanning electron micrograph revealing the microstructured surface of the stamp.

wafer (Figure 1b) such that the devices in contact with the elastomeric stamp break free from the source wafer. The transfer stamp is now populated with devices. Next (Figure 1c), the populated stamp is aligned to and brought into contact with the target substrate. Then (Figure 1d) the stamp is lifted from the target substrate such that the devices are transferred to the target substrate. This transfer process is possible because the adhesion of the device to the elastomeric stamp is dependent on the peel rate of the stamp14. In addition to this kinetic control of the adhesion, a spin-on polymer is used on the target substrate to enhance the yield of the printing process. Next (Figure 1e), the stamp returns to the source wafer and steps to the next set of devices. Then the stamp returns to the target substrate and prints the devices. The process then repeats until the target substrate is fully populated with devices. The transfer process is massively parallel. The transfer stamp shown in Figure 3 prints 2850 die per transfer

operation. The process also allows for the source wafer material to be used in an efficient manner. Figure 4 illustrates the “geometric magnification” that transfer printing enables. By appropriately designing the source wafer and stamp, it is possible to pick-up only one out of every “n” devices. As a result, when operated in this “step and repeat” fashion, a dense array of devices on the source wafer can be transferred into sparse arrays on the target substrate. Yield & placement accuracy Several studies have been performed to evaluate the transfer printing yield and placement accuracy. Two separate chip designs were evaluated. In both cases, the starting source wafers were SOI with a 5 µm thick device silicon layer and a 1 µm thick buried oxide layer. A single photolithography step was performed to define the chip and tethers. Reactive ion etching (RIE) with SF6 chemistry was used to etch through the device silicon down to the buried oxide layer. The buried oxide layer was removed using concentrated hydrofluoric

Global Solar Technology South East Asia – Spring 2010 – 7

Transfer printing: an emerging technology for massively parallel assembly

Figure 4. (a) Schematic illustration of a source wafer consisting of densely packed devices and (b) a target substrate that is sparsely populated with transferred devices. (c) An image taken on the printer showing a source wafer following a single transfer operation and (d) an electron micrograph of the printed chips on the target substrate.

Figure 6. Scanning electron micrographs of transfer printed silicon chips.

acid. Following the sacrificial etch process the photoresist was stripped. In the first design, the chip dimensions were 450 µm x 40 µm x 5 µm. It is worth noting that traditional serial assembly equipment using vacuum tooling would face major challenges handling chips with this form factor2. The transfer stamp (example shown in Figure 3) consisted of a 30 x 95 array of molded elastomeric posts. For this design, each transfer operation prints 2850 chips. Figure 5 shows two examples of 100% transfer yield that were demonstrated. Figure 5a shows the 450 µm x 40 µm chips

printed onto a 100 mm silicon target wafer coated with a spin-on polymer. Figure 5b shows the same chips printed onto a plastic sheet coated with an adhesive layer. Figure 6a and 6b show scanning electron micrographs of these 450 µm x 40 µm chips printed onto a target silicon wafer. Using a very conservative estimate of one transfer operation per minute, the throughput of the transfer printing would be in excess of 170,000 chips per hours. It is conservatively estimated that future generation printers will have cycle times less than 20 seconds per transfer print operation, and should enable throughputs of ~1M chip

8 – Global Solar Technology South East Asia – Spring 2010

Figure 5. (a) Image of a silicon target wafer populated with 2850 chips in a single transfer operation and (b) an image of flexible plastic sheet target substrate populated using the same chipset. The transfer yield was 100% in both cases.

placements per hour. The second design consisted of chips that were 167 µm x 50 µm x 5 µm. In this case the stamp transferred a 16 x 16 array (256 chips) per transfer operation. The transfer printing operation was repeated four times to fabricate a seamless 32 x 32 array of 1024 chips. Figure 6c and 6d show electron micrographs of the printed chips. The tether fracture surfaces are visible in both Figure 6b and 6d. Figure 7 shows a yield map for the 1024 chip array. To measure the placement accuracy of the printer, target wafers were prepared with a reference pattern. In this case, 150 mm glass wafers were patterned with a 500 Å Ti layer using a lift-off process with negative acting photoresist. A 3 µm layer of benzocyclobutene (BCB) was applied to the wafers before transfer printing. In this case, the target wafers were populated with the 167 µm x 50 µm x 5 µm chips. Figure 8 illustrates the metrology method used to measure the placement accuracy. First, the camera on the printer is used to store images of the printed chips and metrology marks. An automated routine is used to compute and subtract the background, convert the image to black and white, and locate objects. A sort algorithm is used to distinguish between chips, metrology marks and foreign objects (dust, debris). Finally, the chip placement accuracy (Δx, Δy, Δθ) can be calculated by comparing the located centroids of the chips relative to the centroids of the metrology reference marks. The results of performing the metrology can be plotted in various ways. Figure

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Transfer printing: an emerging technology for massively parallel assembly

9 shows a placement accuracy vector plot. The consistent displacement vector patterns indicate that a slight rotational (θ) misalignment occurred during each transfer print. Figure 10 displays the same data in a color-coded plot. In this case the magnitude of the displacement vectors is converted to a color scale. The slight rotational error is again apparent in this graph. Finally, the combined X and Y placement accuracy data are shown on a histogram plot in Figure 11. A Gaussian curve fit of this data set indicate that placement accuracy better than ± 4 µm @ 3σ can be achieved using transfer printing with an elastomeric stamp. The keys to achieving this placement accuracy include the ability to manufacture a mechanically stable highfidelity transfer stamp and the ability to align the chips to the substrate by looking through the transparent stamp. This allows for the alignment to be performed with the chips in close proximity to the target substrate. Following the transfer printing, the wafers went through a BCB soft cure

Figure 7. Transfer printing yield map. One chip was missing from this 1024 chip array, which translates to 99.9% yield.

Figure 9. Placement accuracy vector plot illustrating the slight rotational misalignment that occurred on this sample.

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process (210 °C for 40 minutes under flowing N2). Following this thermal process, the printed chips pass scotch tape tests, and standard wafer processing can be performed without disturbing the devices. Measurements revealed that there was no change in the chip placement following the BCB soft cure process. Applications of transfer printing One of the advantages of the transfer printing approach is that all of the demanding fabrication steps for high performance semiconductor devices can take place on the source wafer instead of the target substrate. As a result, the inherent mechanical and chemical instabilities of the target substrate material (i.e. glass, plastic, paper, etc.) do not limit the choice of the semiconductor process or device type. This implies that transfer printing is an attractive method for the manufacture of display or sensor backplanes on glass or plastic. For display applications, transfer printing could be used to print high performance driver circuitry for advanced pixel concepts. It is

anticipated that transfer printing could be applied to the manufacture of advanced backplanes for flat panel x-ray detectors where each pixel requires an amplifier circuit to lower noise15. In the concentrated photovoltaics (CPV) industry, standard assembly equipment is being used to pick-and-place small high efficiency compound semiconductor solar cells16. There is a general trend toward handling ever-smaller solar cells, but current assembly technology places constraints on the numbers and sizes of cells that can be economically handled. Transfer printing opens a path to large assemblies of precisely positioned microscale high efficiency solar cells. Electronic packages, such as Freescale’s Redistributed Chip Package17, require transfer of many die onto a reconfigured wafer. With transfer printing, the package designer could consider assembling smaller devices and the improved placement accuracy would allow for interconnections with tighter tolerance and higher yield.

Figure 8. Methodology to determine the placement accuracy of the transfer printed chips using image analysis.

Figure 10. Placement accuracy color plot. The color scale bar units are microns.

Figure 11. Placement accuracy histogram plot.

Global Solar Technology South East Asia – Spring 2010 – 9

Transfer printing: an emerging technology for massively parallel assembly

Conclusions Transfer printing is a promising new technique for applications requiring high accuracy assembly of large numbers of microscale devices. Unlike traditional assembly approaches that use vacuum chucking, transfer printing utilizes a microstructured elastomeric stamp to both pick-up and place microscale devices. Here, we demonstrated transfer printing of 5 µm thick silicon chips with high yield (> 99%) and accuracy (< ± 4 µm @ 3σ). Acknowledgements The work presented here was partially supported through an NSF SBIR program on flexible display backplanes (NSF IIP0712017). References 1. M. B. Cohn, K. F. Bohringer, J. M. Noworolski, A. Singh, C. G. Keller, K. Y. Goldberg, R. T. Howe, “Microassembly technologies for MEMS,” in Proc. SPI E Micromaching and Microfabrication, Santa Clara, CA, Sept. 20 – 22, 1998, pp. 2 – 16. 2. W. Zesch, M. Brunner, and A. Weber, “Vacuum tool for handling microobjects with a nanorobot,” in International Conference on Robotics and Automation, April 1997, pp. 1761. 3. H.-J. J. Yeh and J. S. Smith, “Fluidic assembly for the integration of GaAs light-emitting diodes on Si substrates,” IEEE Photon. Technol. Lett., vol. 6, 1994, pp. 706 – 708. 4. U. Srinivasan, D. Liepmann, and R.T. Howe, “Microstructure to substrate selfassembly using capillary forces.” Journal of Microelectromechanical Systems, vol.10, 2001, pp. 17 - 24. 5. E. Menard, K.J. Lee, D.-Y. Khang, R. G. Nuzzo and J.A. Rogers, “A printable form of silicon for high performance thin film transistors on plastic substrates,” Applied Physics Letters, 84(26), 5398-5400 (2004). 6. J.-H. Ahn, H.-S. Kim, K.J. Lee, Z. Zhu, E. Menard, R.G. Nuzzo and J.A. Rogers, “High Speed, Mechanically Flexible Single-Crystal Silicon Thin-Film Transistors on Plastic Substrates,” IEEE Electron Device Letters, 27(6) 460-462 (2006). 7. J.-H. Ahn, H.-S. Kim, K.J. Lee, S. Jeon, S.J. Kang, Y. Sun, R.G. Nuzzo and J.A. Rogers, “Heterogeneous Three Dimensional Electronics Using Printed Semiconductor Nanomaterials,” Science, 314, 1754-1757 (2006). 8. D.Y. Khang, H. Jiang, Y. Huang and J.A. Rogers, “A Stretchable Form of Single Crystal Silicon for High Performance

Electronics on Rubber Substrates,” Science, 311, 208-212 (2006). 9. Y. Sun, S. Kim, I. Adesida and J.A. Rogers, “Bendable GaAs Metal-Semiconductor Field Effect Transistors Formed With Printed GaAs Wire Arrays on Plastic Substrates,” Applied Physics Letters 87, 083501 (2005) 10. Y. Sun, E. Menard J.A. Rogers, H.-S. Kim, S. Kim, G. Chen, I. Adesida, R. Dettmer, R. Cortez, and A. Tewksbury “Gigahertz Operation in Mechanically Flexible Transistors on Plastic Substrates,” Applied Physics Letters 88, 183509 (2006). 11. K.J. Lee, M.A. Meitl, J.-H. Ahn, J.A. Rogers, R.G. Nuzzo, V. Kumar and I. Adesida, “Bendable GaN High Electron Mobility Transistors on Plastic Substrates,” Journal of Applied Physics 100, 124507 (2006). 12. M.A. Meitl, X. Feng, J. Dong, E. Menard, P.M. Ferreira, Y. Huang and J.A. Rogers, “Stress Focusing for Controlled Fracture in Microelectromechanical Systems,“ Applied Physics Letters 90, 083110 (2007). 13. E. Menard, J. Park, S. Jeon, D. Shir, Y. Nam, M. Meitl and J.A. Rogers, “Micro and Nanopatterning Techniques for Organic Electronic and Optoelectronic Systems,” Chemical Reviews 107, 11171160 (2007). 14. M.A. Meitl, Z.-T. Zhu, V. Kumar, K.J. Lee, X. Feng, Y.Y. Huang, I. Adesida, R.G. Nuzzo and J.A. Rogers, “Transfer Printing by Kinetic Control of Adhesion to an Elastomeric Stamp,” Nature Materials 5, 33-38 (2006). 15. J. P. Lu, K. Van Schuylenbergh, J. Ho, Y. Wang, J. B. Boyce, R. A. Street, “Flat panel imagers with pixel level amplifiers based on polycrystalline silicon thin-film transistor technology,” Applied Physics Letters, 80, 4656 (2002). 16. Concentrator Photovoltaics edited by A. Luque, V. Andreev, Springer-Verlag, Berlin Heidelberg, 2007. 17. B. Keser, C. Amrine, T. Duong, O. Fay, S. Hayes, G. Leal, W. Lytle, D. Mitchell, R. Wenzel, “The Redistributed Chip Package: A Breakthrough for Advanced Packaging,” Proc. Elec. Comp. Tech. Conf. (57th ECTC), Reno, NV (2007).

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Dr. Christopher A. Bower is Senior Research Scientist at Semprius Inc., where he works on the heterogeneous integration of compound semiconductors with silicon integrated cirucits. He previously held positions at Inplane Photonics as a senior process development engineer and as a scientist at RTI International, where he served as the technical lead on multiple DARPA-funded 3D integration programs. Dr. Bower has authored or co-authored over 40 peer-reviewed publications and holds 2 U.S. patents. Dr. Philip Garrou is a consultant in the field of thin film microelectronic materials and applications, prior to which he was director of technology and new business development for Dow Chemicals’ Advanced Electronic Materials business. He has authored two microelectronics texts and is co-author of over 75 peer reviewed publications and book chapters. Etienne Menard, Founding Scientist, obtained a PhD degree in Chemistry at the University “Pierre et Marie Curie” (Paris, France) and the Department of Material Science and Engineering at the University of Illinois at UrbanaChampaign (UIUC) under the direction of Denis Fichou at the “Laboratoire des Semi-Conducteurs Organiques” (CEA/SACLAY, France) and Prof. John A. Rogers at UIUC. He received an engineering diploma in Electronics from the National Polytechnic Institute of Engineering in Electrotechnology, Electronics, Computer Science and Hydraulics (ENSEEIHT) at Toulouse (France) in 2002. His research has been featured on the covers of recent issues of Applied Physics Letters, Physics Status Solidi A, Advanced Materials and others.

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Solar cells on ultra-thin crystalline silicon

KIC ON BOARD

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Global Solar Technology South East Asia â&#x20AC;&#x201C; Spring 2010 â&#x20AC;&#x201C; 11

Converting considerations for flexible materials

Converting considerations for flexible materials by Josh Chernin, Web Industries, Boston, MA, USA The thin-film photovoltaic (TFPV) industry is beginning to scale up. Hundreds of millions of dollars are being invested in production facilities. Much attention is going to the front-end (the chemistry, physics and efficiencies of the films and the production of the films themselves) and to the back-end (integration into finished products and utilityscale installations, and retail economics), but sometimes less attention is paid to the steps in between, including the converting of the flexible materials. This article will examine some of the more important considerations that go into these intermediate process steps, including technical and economic aspects, some of the hidden costs, and the pros and cons of outsourcing this important suite of manufacturing capabilities. Keywords: Flexible Materials, Slitting, Sheeting, Spooling, Printing, Coating, Laminating, Die Cutting

‘Converting’ refers to the manipulation and finishing of flexible materials. It encompasses processes such as slitting, sheeting and traverse winding; coating, printing (including conductive printing), laminating, and assembly of multi-layer substrates; die-cutting, encapsulation, and similar processes. Other industries have failed to consider these aspects of the process until it was too late to design for optimal manufacturability and lowest cost. Avoiding this error will be especially important in industries such as TFPV, where the substrates are generally produced at fixed widths and require conversion before integration into final production. The best place to start is ‘with the end in mind.’ TFPV companies should consider the entire range of end-products they plan to bring to market before designing their converting capabilities. They should build as much flexibility into converting capabilities as possible in order for this function not to be a bottleneck in either production efficiencies or in the ability to bring products with new configurations into the market. So, for example, in choosing a method of sheeting, they may want to consider having both programmable blades in the machine direction and a programmable guillotine in the cross-machine direction. This combination will provide almost any size sheet. Similarly, those TFPV companies that are using glass as a carrier may find that this limits flexibility downstream and may want to consider a true roll-to-roll process. In general, the thin-film products need to be kept clean and should be run in a cleanroom. Static needs to be minimized, because it will attract dust. Plastic cores should be made of materials that don’t cause static, or coated with anti-stat coatings; rewinds with various cores ‘clutching’ at different rates are notorious sources of static. Some films are sensitive to arcing caused by static electricity, and there are a number of methods to deal with that. Some are sensitive to humidity; they can literally grow in a humid environment. Other considerations include the quality of slitting, especially the quality of slit edges. Slitter dust needs to be minimized by careful

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selection of blade geometries and depths, and sometimes by either contact- or noncontact web cleaning systems. Thin films are susceptible to dusting, especially hard-coated films, and they are also subject to some edge fracture. Dusting causes subsequent problems in downstream operations such as printing, coating and laminating, and fracture can sometimes be fatal to the performance of the films. In addition, belling (lipping at the edges of a slit roll, indicating uneven rewind tension, unsupported edges in the slitting process or uneven blade depth) can put a permanent ‘set’ into rolls that cannot be erased or easily dealt with. Rewind tensions need to be high enough to insure the integrity of the package, while low enough to not deform the materials. Metals can generally be rewound at higher tensions than films. When the converting of TFPV requires coating, printing or laminating, it is important to recognize the differences in the requirements of these materials versus what might be expected from more common flexible substrates. The printing and coating that people are more familiar with are often trying to achieve an aesthetic objective that can be subjective. This is not the case when you are trying to accomplish functional electrical properties. The materials being printed or coated and the coatings being applied are often novel and unique and have been developed to produce specific effects. Whenever possible, the chemistry being applied should be modified to promote its uniform metering and transfer throughout the metering and application process. Many coatings are developmental and have been formulated for electrical properties without regard to the rheology and surface energy needed for optimum transfer and leveling needed for printing or coating. Firms should select methods that don’t compromise the sometimes delicate properties of the base substrate or the functional characteristics of the ink or coating. Printing and coating methods that achieve a degree of shear during the metering process will achieve a smoother and more uniform result, but one must be careful that this does not negatively

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‘Printing’ PV electrodes onto flexible substrates Converting considerations for flexible materials

Figure 1. Laminating, zone-coating and slitting of multiple materials.

impact the performance of the coating or ink. Surface preparation is equally important. Thorough web cleaning may be necessary, as well as surface energy modification by the use of corona- or plasma-treating to promote adhesion. It should be confirmed that any method chosen for improving the surface does not damage the functionality of the surface. This is also true for the method selected for drying or curing the coating or ink. Many coatings used to produce TFPV products are thermally sensitive, and care must be taken to not generate too much heat during this step. If contact pressure is a sensitivity for the materials being processed, a non-contact method should be considered, such as curtain coating or the use of application by ink jet. When laminating, avoid any excess pressure that might produce mechanical work to the coatings as they go through the laminating nip. If air entrainment is a concern, consider the use of smaller diameter nip rollers. Materials slit to narrow widths can be ‘spooled,’ or wound transversely on a core many times wider than the slit width of the materials. This provides a more stable package and enables much longer lengths

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of material to be slit onto each package—sometimes 20-50 times longer than can be achieved with traditional pancake rolls. This in turn benefits the economics of downstream operations, since each roll changeover represents downtime and waste. One aspect to monitor in spooling is not introducing camber (curl) into the material. The spiral-winding methods can introduce camber, especially with metals and at the edges of the spools, but this can be controlled through careful design of the spool configurations, tensioning systems and winding patterns. The spooling example above is a nice segue into discussing the economics of converting operations for two reasons. First, it shows how both the incoming and finished configurations can affect converting costs. In general, converting is a service operation. Although a few converters will offer supply-chain management (purchasing of materials and vendor management) and a few will offer ancillary manufacturing services such as assembly, the economics of the manufacturing services, including converting, are generally driven by time rather than materials. Thus, longer incoming and outgoing lengths drive costs down, as does volume. Width

doesn’t matter as much, since width affects time only in a small way—but this can work to the advantage of a customer too, since adding width doesn’t add much to costs. Spooling’s major converting cost advantage over traditional ‘pancake’ winding is the much longer rewind lengths, which greatly reduce changeover time for the converter. There are many ways in all converting operations to design configurations to best advantage. The second lesson spooling shows about the economics of converting is that the entire chain of events must be considered. Narrowly viewed, the economics can be deceiving; the direct converting costs often hide the value. For example, the direct costs of spooling can often be more than totally compensated for by the lowered downtime and waste associated with fewer changeovers in the next manufacturing steps. Another very important economic aspect is waste. Materials are often so valuable that even a small percentage of waste can outstrip the entire converting cost. A great deal of attention needs to be paid to minimizing waste. Methods include proper configuration, converting techniques and machine design, and the use of low cost

Global Solar Technology South East Asia – Spring 2010 – 13

Converting considerations for flexible materials

Figure 2. A configurable machine capable of performing multiple processes is any order.

leader and trailer materials for startup and shutdown. Typically, in an outsource converting program, there will be five to ten opportunities through the whole chain of events to affect the cost, with the end result being that your outsource partner delivers demonstrable value over and above the simple cost.

FPV companies in this market will need to decide how much, if any converting to perform themselves and how much to outsource. This is a question with strategic as well as tactical implications. A few of the more important factors are: • Does the company have real expertise in thin-film converting? • Does the company want to invest in the assets and devote the space? • How does the company want to devote its time and talents? • Can the assets be fully utilized at the volumes projected? • Can the outsource partner really be considered a ‘partner’? Will they protect important intellectual property? Will they be responsive to needs, and have they proven that they can and will make continuous improvements? Each manufacturer of solar thin films may choose to answer the question of whether to outsource in a different way. Some companies will adopt a hybrid model; for example, keeping in-line converting processes in-house while outsourcing some of

the more difficult processes, perhaps trials, and those where asset investments cannot be justified. There are also a large number of considerations to review in choosing an outsource manufacturing partner. Perhaps the most important, as mentioned above, is whether they would really be a ‘partner.’ Good outsource manufacturing firms will assist TFPV firms in designing a product for manufacturability, which means they should be involved as early as possible. They will bring together available technologies with their own expertise and design a program that makes sense. They will procure materials and manage the vendors. They will demonstrate good listening skills. And they will have the people, technology, capital and MIS resources to pull it off, and to continuously improve the performance. Of course, cost is a major consideration. However, TFPV companies are well advised to think in terms of ‘value’ rather than ‘cost.’ Narrowly viewed, internal direct costs almost always beat outsourced costs. But viewed on an end-to-end basis, a good outsource vendor will deliver more value than cost. For example, their direct cost of slitting may be higher, but if their waste factor is lower, the cost may well pay for itself. Playing ‘bank’ for their customer (by fronting the cash needed to pay for subtier vendors’ materials) can free up needed cash. Simply eliminating various hassles such as managing vendors and expediting materials has value as well. Other considerations in selecting an outsource converting vendor are: • geographic reach, number of

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facilities • a bility to line up information systems with the customers’ • traceability of material • registration to international quality standards (ISO 9001 being the minimum standard) • ability to purchase materials to spec and to manage the subvendors • ability to purchase outside services and to manage those sub-vendors Finally, a most important consideration in choosing an outside converting partner is the extent in which the customer trusts that the converter will protect intellectual property. IP is often the most valuable asset that a TFPV owns. The converter should be able to demonstrate that they employ legal, physical and MIS protections that will safeguard this knowledge. It is not enough to simply sign a CDA.

Josh Chernin is the general manager of Web Industries’ Boston facility. Web Industries is a leading provider of outsourced flexible material manufacturing services, with six plants in the United States. Services include slitting, sheeting, spooling, printing, coating, laminating and die cutting, as well as supply chain management and assembly. Josh can be reached at jchernin@webindustries.com.

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‘Printing’ PV electrodes onto flexible substrates

Delhi International Renewable Energy Conference Expo Centre - Expo XXI, National Capital Region of Delhi

27-29 October 2010 l 600 Exhibitors l 5,000 Conference delegates l 250 High profile

speakers l 20,000 Trade Visitors l 40 countries

Organiser

Managed by

Exhibitions India Group IOS 9001:2008 & ISO 14001:2004

Government of India Ministry of New & Renewable Energy

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Rajneesh Khattar, Tel: +91 11 4279 5054 M: +91 98717 26762; rajneeshk@direc2010.gov.in

www.direc2010.gov.in Global Solar Technology South East Asia – Spring 2010 – 15

Materials and the growth of PV technology

Materials and the growth of PV technology David A. Preische, Indium Corporation of America, Utica, NY, USA The solar industry has grown tremendously over the last few years, driven by government subsidies and concerns over rising oil prices, increased air pollution and global warming. This has resulted in a significant increase in the cost-per-unit of energy. The primary goal for the solar industry is to optimize economies by adding capacity and reducing the cost per watt produced by a solar cell. This goal has been difficult to achieve due to a shortage of key materials and components, reliability issues of existing and new materials, and various challenges in commercializing innovative manufacturing technology.

Keywords: CIGS, Solar, Indium, Gallium, Silicon, Tabbing Ribbon This paper was originally presented at SMTAI 2008.

Introduction Photovoltaic technology is generally classified into two categories: silicon wafer and thin film. Silicon wafer includes polycrystalline and single crystal silicon technologies, and these technologies have been around for decades. Together they account for over 95% of solar cell production today. Thin Film technologies can be broken down further into four categories: amorphous Si (a-Si), crystalline silicon on glass (CGS), cadmium telluride (CdTe) and copper-indium-gallium diselenide (CIGS). Thin film technologies emerging today have the greater potential to offer the lowest cost-per-watt at the module level. Market growth The overall demand for solar over a five-year period from 2006-2010 is estimated at 52% CAGR, from 2,000 MWp to approximately 11,000 MWp.

Geographical market distribution Germany continues to lead the way in MWp fueled by government incentives, specifically a feed-in tariff (FIT) program whereby the owner of a solar system is paid for electricity generated by the system whether it is consumed or fed back to the grid. This contrasts with a net-metering incentive, which measures the difference between the total amount of electricity generated and what is actually consumed.

CIGS CIGS technology offers the greatest probability for low cost PV energy generation due to higher cell efficiencies and total system costs. As a result, this technology continues to emerge, led by companies such as Miasole, Showa-Shell, Honda Soltec, Wuerth, Solyndra, Nanosolar, Q-Cells, Solibro, SoloPower and many others. There are primarily four competing process technologies for development of a CIGS solar cell: 1) sputtering using a planar or rotatable target of CIG or alloy combination, 2) printing using an alloyed powdered metallurgy with gallium applied using a screen printer, 3) plating using an electrochemical plating solution and 4) evaporation or co-evaporation using a CIG elemental or alloy composition. Material concerns Indium The most prominent discussion over the past few years regarding material availability has been in relation to the metal indium. Indium usage in 2007 is estimated at approximately 1300 metric tonnes (mt). Approximately 75% is used within the FPD industry to coat glass with indium-tin oxide for LCD and plasma TVs, laptop computers, monitors, cell phones, etc. The remaining 25% is used in manufacturing processes for alkaline batteries, CIGS solar cells, semiconductors, thermal-interface materials, and for a variety of niche soldering applications. Indium, a by-product of zinc, is 3x more abundant than silver. More than 50% of

Figure 1. PV demand by technology.

Figure 2. Global PV demand.

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Figure 3. CIGS technology growth.

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Materials and the growth of PV technology

Supply --- Demand --- Avg Price ---

Figure 4. Price history—indium.

the indium used today, on an annual basis, is reclaimed and placed back into the supply chain. Virgin indium is extracted from zinc as direct result of demand. For CIGS, demand is based upon MW output. For every 1 MW of CIGS based solar cell production, 60 kgs of indium is consumed. By 2010, this equates to approximately 60 mts, <5% of the total indium demand for the same time period. Therefore, the FPD market is expected to remain as the dominant application using indium for years to come. As this market is considered more predictable (allowing supply to meet demand) versus five years ago when demand spiked as a result of LCD and plasma displays, meeting demand for all applications, including CIGS solar, is of less concern. Additionally, the continuous improvement in reclaim efficiencies and cycle times will further ease the necessity for virgin indium extraction. To avoid any temporary material supply shortages it is essential that good communication exists relative to forward demand between the users and indium suppliers. The issue is less about the availability of indium and more centered on the availability of information (of future demand). there may be periods of intermit Although

Figure 5. Indium supply chain.

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tent volatility, long term there are no supply concerns.

Gallium Gallium is extracted from bauxite, which has no supply concern. It is used in applications including GaAs devices, LEDs and solar cells. The availability and hence supply of gallium is only limited by the capacity of existing facilities to increase output. The primary driver for investment in increasing output is based upon the economies associated with its price level. At the time of this writing, gallium is considered to have stable supply in relation to demand. It is plentiful with possible periods of intermittent volatility.

“Short term bottlenecks exist in the supply of key components. Alignment of technology, product development and capacity roadmaps between manufacturers and suppliers is critical for success.” Silicon Silicon-based technology remains the domi-

nant technology for PV supply, roughly 90%. Although Si is currently experiencing a supply imbalance, which has resulted in an escalation of price, this is expected to be overcome as additional capacity comes online in 2008 and 2009. Tabbing ribbon Typically a Cu cored and solder tinned (pb free or standard Sn/Pb alloys) tabbing ribbon is used to interconnect solar cells while creating the least amount of resistance between them. The key concerns revolving around tabbing ribbon are availability and quality. Typical lead times range from two months to as long as four months. Additionally, from a material quality perspective, achieving a low camber value is problematic. Custom sputtering targets for CIGS As CIGS is an emerging technology, it is common that each company has a unique approach to developing the absorber layer. As such, each user has a unique alloy combination and composition that may result in forcing the supplier into a ‘trial and error’ mode of fabrication. Metallization pastes/inks for CIGS Very few metallization pastes/inks for CIGS exist on the market today, in combination with very few companies operating in a production mode. This of course will change over time. Additionally, each company has a proprietary process that inhibits the flow of information relative to specific process parameters in which the material must perform. The challenge becomes hinged with suppliers’ ability to quickly develop new materials designed for the unique process environment. Conclusion The growth of PV technology and hence production and capacity is forecasted Continued on page 18

Figure 6. Gallium supply chain.

Global Solar Technology South East Asia – Spring 2010 – 17

Interview How Sanmina-SCI determined its alternative energies strategy

Interview

Paul van der Wansem— BTU International For decades, BTU international has been a leading supplier of advanced thermal processing equipment for electronics manufacturing, which includes printed circuit board solder reflow and semiconductor packaging applications as well as, for the past 15 years, thermal processing systems to the solar manufacturing industry. This year, the company has expanded in the emerging alternative energy market with new process equipment for solar cell manufacturing, in addition to its existing products for nuclear fuel processing and the production of fuel cells. The expansion includes the creation of a new Alternative Energy Business Group and two new, high-level appointments. John J. McCaffrey, Jr., has been appointed vice president of alternative energy in charge of engineering and product development, and Douglas Lawson has joined BTU as vice president of alternative energy in charge of marketing and business development. The company celebrated the opening of a new solar research and processess application laboratory in Shanghai, China, this year. Another is in the works closer to home, in Billerica, Massachusetts. Global Solar Technology recently spoke to BTU’s chairman, president and chief executive officer Paul Van der Wansem, about the change in the company’s focus and how we might expect to see the company evolve over the coming years. Q1: We’ve been hearing a lot about BTU in the solar market. How will your focus on solar cell processing effect your electronics assembly business? Without question, the electronics assembly business is vitally important to BTU. It currently represents the majority of BTU’s business, and it will for some time. However, anyone who watches the electronics industry can tell you that its cyclicality can be a challenge to manage. We hope that by diversifying into alternative energy applications we can achieve a healthier balance of business. This will directly benefit our electronics assembly business by allowing us to maintain a larger corps of engineering and development staff, and will keep our factories and supply chains running smoothly, regardless of the business cycle—not to mention enabling us to maintain and even expand our customer service and support infrastructure. We are currently increasing our headcount by almost 10 percent, with many of the new hires coming in the engineering and development area. Process-wise, there are a lot of similarities between the thermal steps for solar and electronics assembly. We hope to apply future technology breakthroughs to both

BTU’s Paul va der Wansem, chairman, president and CEO.

markets. Also, for both markets we have an intense focus on reducing total cost of ownership and are focusing our engineering efforts in this area. For solar, reducing the cost per watt is vital to the industry’s growth and sustainability. In electronics, cost pressure is not new and is something we work on constantly. We are proud of

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our industry-leading Pyramax products that provide significantly reduced cost of ownership, achieved through a focus on uptime, and reduced nitrogen and power consumption. Our latest Pyramax product, introduced at APEX 2008, is the Pyramax 75A, which has extremely low running costs.

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Interview

Q2: Can you tell us how it is going for BTU in the solar business? During the past year we have increased the pace of our transformation into a process equipment company that serves the emerging high growth alternative energy industry while continuing to serve our traditional business in electronics. Recently we created a new Alternative Energy Business Group and more than doubled revenues and increased bookings by 2.5 times in the solar segment compared to 2006. We added two new executives with strong backgrounds in both solar technology and business development. In addition, we recently opened a new Photovoltaics Process Center within our facilities in Shanghai, China, and are establishing a second such laboratory in Billerica, Massachusetts. These facilities will be used to develop new solar process capabilities and provide an environment where customers can process photovoltaic devices—both silicon and thin film-based— on BTU systems. The Shanghai Photovoltaics Process Center is operated with our partner in metallization, DEK. Q3: Why did you choose to focus on alternative energy? A: Our decision to focus on alternative energy business as a prime driver for our growth was based on several key factors: • The need for new energy—especially renewable, clean energy—has resulted in a large market demand; • BTU has many core technologies

and significant know-how that are applicable to processing devices used to generate alternative energy; and • over the years we have built a strong global support network with key engineering and manufacturing capabilities in Asia and the USA. These strengths will serve as a base from which we will address the worldwide demand for process equipment used in Energy generation applications. And as mentioned previously, we are welcoming the opportunity to balance and diversify our business, thereby strengthening our infrastructure in good times and in bad. Q4: What is the outlook for BTU? Looking forward, we see 2008 as an exciting and challenging year. We expect to continue to develop new products and technologies for both the electronics and alternative energy markets. As I mentioned, we are aggressively expanding our workforce and investing heavily in the kinds of new products that will support our growth in the years ahead. We believe that the course we are on is the best way for us to support our customers’ needs—whether in electronics or alternative energy—and the best way to enhance our investors’ value. We see it as a win-win situation. Thank you, Paul. —Trevor Galbraith

Materials and the growth of PV technology— continued from page 17

at 52% CAGR. The key drivers for the explosive nature of this market include the increasing cost of oil and coal, government incentives such as net metering and feed-in tariffs, global warming and reducing carbon footprints. This demand has brought forward concerns over material availability, consistent quality and supplier capability to customize (and deliver quickly) as well as product performance. Indium, gallium and silicon may continue to experience periods of intermittent volatility but are sustainable for all associated applications for the foreseeable future. As the technology matures, particularly for thin film solar module production, products and processes will be optimized resulting in the reduction in total system cost lending to the ultimate goal of PV energy, to reach a cost level that is competitive with the grid. References 1. Gregory Phipps, Claire Miko, Terry Guckes, Indium Corporation of America, “Sustainability of Indium & Gallium” 2008 2. Schwartz-Schampera, Herzig, Roskill Indium Geology 3. Deutsch Bank, Solar Photovoltaic Industry, “Solar PV industry outlook and economics”, 27 May 2008 David A. Preische is Indium Corporation’s director of sales for metals, chemicals, & energy. David describes Indium’s participation in photovoltaic cell manufacturing as an outgrowth of their metals and chemistry business, a business that has been in operation for quite a while beside Indium’s Electronics Assembly Solder business unit.

BTU International’s integrated In-Line Diffusion System for phosphorous diffusion of solar cell wafers.

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Global Solar Technology South East Asia – Spring 2010 – 19

Atmospheric plasma surface modification for continuous processing of solar cells

Atmospheric plasma surface modification for continuous processing of solar cells by Rory A. Wolf, Enercon Industries Corporation, Menomonee Falls, Wisconsin, USA The use of plasma surface modification technology in photovoltaic cell manufacturing has heretofore been used primarily in applications such as the deposition of amorphous hydrogenated silicon nitride (SiN) layers in a vacuum plasma-enhanced chemical vapor deposition (PECVD) process to create anti-reflection and surface (and bulk) passivation on thin-film solar cells, or the use of vacuum plasma etching in barrel-type reactors to perform edge isolation in some remaining fabrication processes. As photovoltaic cell manufacturing processes evolve, and with the added pressures of increasing hazardous chemical waste disposal costs, there has been interest in atmospheric plasma systems as efficient dry etching, surface cleaning and adhesion promotion process tools. This paper examines these systems and details etching, cleaning and bonding trial data confirming system efficacies.

Keywords: Solar Cell Processing, Photovoltaic Cell Manufacturing, Plasma Surface Modification

Introduction The use of plasmas in the fabrication of photovoltaic cells is highly dependent upon the materials employed and the processing cycle requirement. For example, vacuum plasmas are not suitable for use in solar cell processing when high throughput on a continuous basis is required. Vacuum plasma chambers built for SiNx deposition are typically batch-process related, but are also designed to work in a semi-continuous mode through the intermittent exchange of treatment materials within the vacuum chamber after the treatment is completed and once atmospheric pressure is returned. However, this process is still not economical for high throughput plasma surface etching, cleaning and functionalization. There are at least four major generations of photovoltaic cells whose materials define the application of plasma technology to their fabrication. They are:

• Large-Area, Single Layer P-N Junction Diode—Typically made using a silicon wafer and the dominant technology in the commercial production of solar cells, accounting for more than 86% of the solar cell market. • Rigid and Flexible Thin-Film Solar Cells—Semiconductor deposition materials used include amorphous silicon, polycrystalline silicon, micro-crystalline silicon, cadmium telluride, and copper indium selenide/sulfide. Typically, the top surface is low iron solar glass for rigid cells (a fluoropolymer for flexible cells), the encapsulant is crosslinkable Ethylenevinyl acetate (EVA), and the rear layer is a Tedlar- PET-Tedlar laminate (although glass, coated PET or another bondable polymeric film are also used). • Photoelectrochemical, Polymer and Nanocrystal Cells—Do not rely on a traditional p-n junction to separate photo-generated charge carriers. Polymer cell materials used include polyester (PET) foil, indium tin oxide (ITO) film, polyethylenedioxythiophene (PEDOT)

20 – Global Solar Technology South East Asia – Spring 2010

and aluminum. Nanocrystalline cells use thin film materials and are overlaid on a supporting matrix of conductive polymer or mesoporous metal oxide. • Composite (Hybrid) Photovoltaic Technology—One example is the use of polymers with nano-particles to make a single multi-spectrum layer which can be stacked to make multi-spectrum solar cells. Bulk silicon technologies, such as those employing wafer-based manufacturing, feature self-supporting wafers between 180 to 240 micrometers thick that are processed and then soldered together to form a solar cell module. Organic and polymer solar cells are built from thin films (typically 100 nm) of organic semiconductors, such as polymers, and small-molecule compounds like polyphenylene vinylene, copper phthalocyanine (a blue or green organic pigment) and carbon fullerness. Considering the wide range of materials employed to maximize solar efficiencies, the ability to integrate the completely continuous in-line manufacturing of rigid panel and flexible solar cells by utilizing a variable chemistry surface modification technique relative to complex material constructions holds the prospect of significantly reducing manufacturing costs. Atmospheric pressure gas phase plasma technology will therefore become essential for future in-line manufacturing of solar cells if major reductions in fabrication costs are to be achieved. Plasma treatment Atmospheric plasma treatment (APT) devices allow for completely homogenous surface modification without filamentary discharges (known as streamers), because a uniform and homogenous high-density plasma at atmospheric pressure and low temperature is produced. In Figure 1, a comparison between corona discharge and plasma is shown. The APT process modifies material surfaces similarly to vacuum plasma treatment processes—the surface energy of treated ma-

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Atmospheric plasma surface modification for continuous processing of solar cells

terials increases substantially, corresponding to enhancements in surface cleanliness, wettability, printability and adhesion properties. The APT process consists of exposing a polymer to a low-temperature, high-density glow discharge (i.e., plasma). The resulting plasma is a partially ionized gas consisting of a mixture of neutral molecules, electrons, ions, excited atomic and free radical species. Excitation of the gas molecules is accomplished by subjecting the gas to an electric field, typically at high frequency. Free electrons gain energy from the imposed high frequency electric field colliding with neutral gas molecules and transferring energy, dissociating the molecules to form numerous reactive species. Interaction of electrons, UV radiation and excited species with solid surfaces placed in opposition to the plasma results in the chemical and physical modification of the material surface. The effect of plasma on a given material is determined by the chemistry of the reactions between the surface and the reactive species present in the plasma. At the low exposure energies typically used for surface treatment, the plasma surface interactions only change the surface of the material; the effects are confined to a region only several molecular layers deep and do not change the bulk properties of the substrate. The surface is subjected to ablation and activation processes (Figure 2). Activation is a process where surface functional groups are replaced with different atoms or chemical groups chosen to react within the plasma. The bombardment of the polymer surface with energetic particles and radiation of plasma produces the ablation

Figure 1. Corona discharge compared with atmospheric plasma between planar electrodes.

Figure 3. Atmospheric plasma micro-etching effect of PE film, 30,000 SEM magnification.

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and micro-etching effects. The bombardment by plasma species is able to create a nano-roughness on a polymeric film, for example, that does not modify the mechanical bulk properties of the film but removes low molecular weight surface organics and thereby strongly increases surface adhesion (Figure 3). Where bond strength is required, atmospheric plasma’s highly reactive species significantly increase the creation of polar groups on the surface of materials so that strong covalent bonding between the substrate and its immediate interface (i.e., coatings, adhesives) takes place. Surface cleaning via atmospheric plasma techniques reduces organic contamination on the surface in the form of residues, anti-oxidants, carbon residues and other organic compounds. Oxygenbased atmospheric plasmas in particular are effective in removing organics whereby mono-atomic oxygen (O+, O-) reacts with organic species resulting in plasma volatilization and removal (Figure 4). Solar cell processes transferrable to atmospheric pressure plasma processes are therefore dry etching, surface cleaning, etching and activation. Layer reductions using hydrogen-based atmospheric glow discharge plasmas is also therefore an employable aspect of the technology. Experimentals As described above there are a significant number of solar technology platforms, many of which are undergoing cost reductions and efficiency improvements to enable or extend their commercial viability. Cleaning and functionalizing the surface of flexible base films and foils in a continuous process prior to panel fabrication to improve thin film adhesions and output efficiencies can be critical in achieving

commercialization. Moreover, as Table 1 outlines, avoiding the use of wet chemical cleaning solutions in favor of ‘green’ process techniques that do not generate VOCs or waste effluents can also significantly improve commercial returns. Given the process benefits of APT above, an experimental was performed employing this continuous process. Referring to Table 2, a microcosm of solar cell base materials were exposed to an APT process for the specified treatment purposes for optimizing interfacial adhesion and improving solar cell output efficiency. The treatment protocols identify the base plasma inert gas chemistry, assisted by a reactive oxygen component, which was determined to optimize treatment results relative to the solar cell application. For example, specific peel adhesion benchmarks were targeted for PVC adhesion to a solvent-base adhesive. Relative to cleanliness benchmarks, pre-specified low level organic particle contamination concentrations were established to optimize lamination adhesions. The required power densities applied to each protocol were predetermined relative to the required surface effect by laboratory trials on commercial roll-to-roll and tangential atmospheric plasma surface treatment systems at the Enercon Industries pilot facility. One specific experimental employed polyimide film which was surface treated by APT at a power density of 20W/ft2/ in using an argon/oxygen plasma. Surface tension was raised from its inherent level of 40 dynes/cm to water wettability, or 72 dynes/cm. Polyimide film was also treated using a reactive silane-based wet chemical primer treatment. Both surface treated films were laminated to aluminum foil and then subjected to a foil strain gauge test. The peel force results in Table 3

Figure 2. Plasma activation of polymer surface by creation of free radicals through substitution.

Figure 4. Micrograph of PET film (a) untreated with low molecular weight organic contamination, (b) after corona discharge cleaning, and (c) after oxygen-based atmospheric plasma cleaning.

Global Solar Technology South East Asia – Spring 2010 – 21

Atmospheric plasma surface modification for continuous processing of solar cells Aluminum Foil Cleaning Process

Caustic Chemical (Wet) Cleaning

APT (Dry) Cleaning

Active Cleaning Agent(s)

Water-base Sulphuric Acid

Ion/Electron/Photon Bombardment

Alkaline Solutions

Inert + Non-hazardous Reactive Gas

Alcohol Solutions Dissolved within Caustic Chemical

Rolling Oils Oxides Water-Soluble Derivatives

Entrained in Process Exhaust

Volatilized hydrocarbon particles Aluminum oxide particles Water-Soluble Aluminum Derivatives

Emissions

Water Laden w/ Chemical Wastes

15 ppm Ozone Inert gas (98%) Reactive gas (90%) <10 ppm CO2 <10 ppm Water Vapor Volatized surface particulates

Recurring Process Costs

Fresh Water, Additional Chemicals

Process Gases

Handling, Disposal Costs Table 1. Wet vs. dry solar cell base material surface cleaning.

indicate a 22% improvement in bonding strength using APT surface modification vs. chemical primer pre-treatment. Conclusion Solar power is a technology of the future. Successful commercialization of low cost, high efficiency fabrications is highly dependent upon fabrication methods that employ continuous processing techniques. One major issue encountered in solar cell construction is the adhesion of thin film solar cells on polyimide substrates. We evaluated the adhesion promotion potential of variable chemistry atmospheric plasma surface modification against wet primer chemistry on a polyimide-based substrate to determine their comparative bonding strengths to aluminum foil. It was apparent that APT is a viable continuous and environmentally friendly process alternative to batch plasma and surfactantbased surface modification protocols. References 1. S. Schaefer, H. Lautenschlager, M. Juch, O. Siniaguine, R. Lüdemann, “An Overview of Plasma Sources Suitable for Dry Etching of Solar Cells”, 28th IEEE Photovoltaic Specialists Conference, Anchorage, September 19-22, 2000. 2. A. Vijh, X. Yang, W. Du, X. Deng, “Film Adhesion in Triple Junction a-Si Solar Cells on Polyimide Substrates”, Dept. of Electrical Engineering and Computer Science, University of Toledo.

Solar Material

APT Surface Treatment Purpose

Treatment Protocol

EVA top-coated PVC

Improve adhesion of solvent adhesive to PVC

Argon/O2 plasma, 343W/ft2/in

Cadmium Telluride

Improve adhesion of cadmium telluride to glass

Argon/O2 plasma, 145W/ft2/in

Unannealed Hydro Foil

Clean unannealed foil surface

Helium/O2 plasma, 40W/ft2/in

Thin film solar cells

Clean foil of organic particles

Helium/O2 plasma, 30W/ft2/in

Aluminum foil

Clean foil for lamination of water-based coatings

Helium/O2 plasma, 30W/ft2/in

Silicon wafer (roll form)

Improve wettability for photovoltaic modules

Helium/O2 plasma, 54.5W/ft2/in

Polyimide film

Improve surface wettability for metal adhesion

Argon/O2 plasma, 20W/ft2/in

Table 2. Base material pre-treatment protocols. Polyimide Strain Gauge Film Metal Adhesion Results Sample

Peel Force

Cadmium Telluride

Improve adhesion of cadmium telluride to glass

Unannealed Hydro Foil

Clean unannealed foil surface

Thin film solar cells

Clean foil of organic particles

Aluminum foil

Clean foil for lamination of water-based coatings

Silicon wafer (roll form)

Improve wettability for photovoltaic modules

Polyimide film

Improve surface wettability for metal adhesion

Table 3. Peel-adhesion comparison of APT vs. chemical primer.

22 – Global Solar Technology South East Asia – Spring 2010

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Interview

GE Renewable Energy global headquarters in Schenectady, NY. (Source: GE)

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Global Solar Technology South East Asia – Spring 2010 – 23

Combating the impact of contamination in solar cell production

Combating the impact of contamination in solar cell production by Sheila Hamilton, Teknek, Renfrew, Renfrewshire, UK

Photo voltaic cell manufacturers today are under increasing pressure to increase yields and improve the efficiency of their products. This has become more imperative as the cost of raw materials has risen dramatically in recent years. One of the main barriers to achieving this is the incidence of contamination in the production environment. If contamination is present before coating, metallization, printing or lamination yields may be affected. This article will look at the impact of contamination, the key sources of contamination and the problems which can arise, and suggests possible solutions to negate the effects of contamination. Keywords: Contact Cleaning, Printing, Contamination, Debris, Yield

How contamination addition, the connec“Conductive materials affects PV module tor circuits face similar production depends problems to first (debris) can result on which of the three generation PV cells in in corrosion of the types of solar cell terms of tombstoning, being produced. blow-outs and short finished product and In first generation circuits, if contaminamay only show up in solar cells—silicon tion is present. Likewafers—the presence wise, at the encapsulathe field later in the of dirt and debris tion stage, the glass or can affect the screen film must be cleaned if product’s life.” printing process, maximum efficiency is leading to problems to be achieved. such as tombstoning, Third generation pin holes, open and short circuits. Contamisolar cells use screen printing techniques nation of solder joints can lead to miniature similar to those employed in the microelec‘blow outs’ as organic materials vaporize and tronics sector. This type of cell generally has expand, rapidly causing voids and dry joints. a lower efficiency than generations one and The solar cell modules are then encaptwo, so it is important that contamination sulated in an EVA film. If dust or particles does not lower the efficiency even more. become trapped between the film and solar The substrate and stencil must therefore cells, it can affect the efficiency of the cells be thoroughly cleaned before each printing by blocking sunlight. Given that efficiencies stage. As the collector patterns become ever are already generally low, this is something finer to produce greater efficiencies, the manufacturers will wish to avoid. Even impact of particles becomes greater. The subparticles too small to be seen, due to a tentstrate used for printing is generally polyester ing effect, can produce visible defects in the film or thin sheet steel. These substrates arlaminated surface (fish eyes). rive for coating or deposition direct from the The second generation of PV cells—vacsupplier and are frequently contaminated uum metalised—are more efficient; however with debris from the manufacturing process. the substrate needs to be cleaned before and For example, rolls of polyester are usually during the deposition chamber process. In slit to a specific width and slitter dust can

PV Technology cSi

Thin Film Technologies

Copper Indium Cadmium Tellurid

Silicon Based

Flexible Substrates

Copper Indium Gallium Diselenid

aSi

Silicon Based

Copper Indium Sulfite

aSi/µcSi

CIS/CIGS

Figure 1. PV tcchnologies.

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Combating the impact of contamination in solar cell production

tive means of removing contamination as the roller makes contact with the surface. Other methods, such as blowers and vacuum systems, cannot cut through the boundary layer of air which sits just above the surface of the substrate. Contact cleaning equipment—both standard and bespoke—is available to suit most PV production environments for both in line (continuous/reel to reel) processing and discreet items, such as wafers.

Figure 2. PV technology roadmap. Courtesy Shiller Automation.

be present on the surface of the material. Statically attracted particles are also an issue for dielectric base materials. It is not only during the manufacturing process that contamination can cause problems. Conductive materials (debris) can result in corrosion of the finished product and may only show up in the field later in the product’s life. So what can be done to minimise the impact of contamination in a PV cell production environment? Many manufacturers are turning to a proven technology from the semi-conductor sector— contact cleaning. Using contact cleaning equipment, it is possible to remove loose particles

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down to one micron in size from a silicon wafer or substrate, such as glass or EVA film, without damaging the surface. The equipment, pioneered by Teknek, uses a special elastomer roller to lift the contamination from the surface and transfer it to a roll of adhesive film for examination and disposal of the debris. When used at each stage of the production process where contamination could be present, contact cleaning equipment can lead to dramatic increases in yields and the efficiency of the PV cell. Contact cleaning methods have proven to be the most effec-

Conclusions With the costs of raw materials rising, it is more important than ever for PV manufacturers to find ways of increasing yield and reducing waste. Contamination has a major impact on both production efficiency and efficiency of the solar cells themselves. By removing contamination using methods such as contact cleaning it is possible to increase yields and improve the efficiency of solar cells.

Sheila Hamilton is technical director and a board director with Teknek, responsible for keeping the company at the forefront of its field in terms of innovation and product design. Sheila joined the company in 1987 as technical director after working as a product designer and power station engineer. She has also run her own consultancy in the field of electronics component packaging. Sheila has a BSc in mechanical engineering from Glasgow University and is currently studying for an MBA at Strathclyde University. She is a recipient of two Smart Awards in the field of Electromagnetic Interference.

Global Solar Technology South East Asia – Spring 2010 – 25

Light of the world

Building success as the solar industry goes global by Darren Brown, DEK, Weymouth, United Kingdom Growing pressure to utilise renewable energy sources is driving up sales of solar panels globally. Under these conditions, current suppliers can achieve rapid growth, and new manufacturers can seize the opportunity to enter the market. Production equipment and techniques are also changing, to deliver higher performing products at high quality and in high volumes.

Keywords: Thin-Film PV Cells, High-Volume Production, Screen Printing

Introduction: Capacity and opportunity Demand for solar panels is greater than current manufacturing capacity. There are several reasons for this. Effective government incentives on renewable energies are encouraging individual homeowners to install generating equipment capable of fulfilling a proportion of the total domestic requirement. Another factor is the trend for high-profile businesses to be seen to commit to sustainable practices. Premises that can support large solar-cell installations, such as a supermarket site, enable these companies to derive an impressive percentage of their energy requirements from renewable sources. Production capacity is increasing, however. Some new projects recently reported by Semiconductor International include the expansion of the QS Solar plant in Shanghai to 75MW, and a new plant of 64MW capacity to be built by Schott Solar in Santa Fe, New Mexico. Since global demand for solar panels is calculated in watts, production planners tend to size a plant to match their ambitions in

terms of market share. Companies can then ‘pay as they grow’ by buying-in extra capacity. This approach also simplifies planning for start-ups. In fact, the barriers to new companies entering this market are currently low. Solar, or photovoltaic (PV), cell technology is relatively straightforward and easy to understand and produce, and the equipment can be planned and installed almost as a shrink-wrapped production line meeting the required capacity. This represents an attractive opportunity for many types of manufacturing businesses with sufficient real-estate to install a production line and suitable management and logistical competencies. Manufacturers in emerging economies are particularly well placed to benefit. Capacity is growing faster in India and China than in other areas. Germany, for example, has the highest total PV manufacturing capacity, but growth is slower than in Asia. Currently there are an estimated 50+ companies producing PV cells in China alone, including indigenous businesses and foreign investors. PV manufacturing techniques There are currently two manufacturing technologies for PV cells. Those fabricated on bulk silicon substrates currently account for more than 90% of global production. These are built up using thick-film production techniques, by depositing an array of fine current-collector fingers on the topside of the substrate, applying an aluminium metallisation layer to the bottom side, and then creating a series of wider bus bars for electrical interconnection purposes. The bus bars are usually deposited as a silver-based compound around 2 mm wide. In this way, the PV cell is built up through a sequence of processes, each of which is relatively easy to implement and control using the latest equipment now emerging to service the growing number of PV cell producers. Thin-film PV technology is a newer alternative, which not only allows cell arrays to be fabricated on silicon but also enables substrates such as flexible polymer, steel or glass sheets to be used. This will allow energy harvesting capabilities to be embedded directly in windows and other panels for of-

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Light of the world

“Historically low sales volumes for PV panels have warranted reliance on bespoke equipment, built to special order, but with the transition to a high-volume global market, capital equipment suppliers must make use of more modern techniques.” fice buildings, warehouses and many other locations. Screen printing is the process of choice for PV cell production. The equipment and processes are robust. Current leading-edge equipment is easily capable of meeting the accuracy and repeatability requirements to produce PV cells at high yield rates. The typical requirements for line width when depositing current collectors on a bulk-silicon PV array, for example, is 100 microns. Some vendors of screen printing solutions are able to achieve significantly greater accuracy. DEK, for example, has a successful track record in the semiconductor packaging industry, and is able to produce interconnects for chip-scale packages using advanced screen printing capabilities. Conversely, screen printing is also effective to produce relatively thick deposits at high speeds. Screen printing also offers benefits in thin-film PV cell production. For example, some emerging techniques to boost energy conversion efficiency will require intricate deposit patterns to produce multiple cell types on a single substrate. These allow the array as a whole to be sensitive to the widest possible range of wavelengths and thereby harvest more energy from light falling on the panel. Screen printing is able to achieve complex deposit shapes to produce these multi-cell arrays at lower cost than other processes, such as vapour deposition and jetting. Accurate design and production of stencils and emulsion screens is critical to the success of screen printing in any precision industrial application. PV cell fabrication is no exception. A number of technologies are applicable, including lasercut or electro-formed metal stencils as well as emulsion screens created by etching the

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required image in a fine, coated mesh. These hold the key to producing a variety of ultra-fine features, heavy deposits or complex patterns in a single operation to sustain continuous high throughput. As consumer demand for solar panels increases, the PV industry’s requirements on resolution, repeatability, flexibility and high-speed throughput are now expected to increase more quickly than at any time in the past. Increasingly, manufacturing businesses will need to ensure that their partners are able to deliver solutions that not only meet current technical requirements but also help them scale capacity quickly and easily in response to rapid developments in the market. Turnkey production line A generic PV cell production line comprises a sequence of printing and drying stages to create the bottom-side metallization, bus-bar, and top-side currentcollector layers. After the final printing stage, the cell is fired in a furnace. At the beginning of the line, a cassette loader delivers the unprinted wafers into the first printer. Subsequent handling includes an automated inverter to allow printing on

Global Solar Technology South East Asia – Spring 2010 – 27

Light of the world

both sides of the wafer, and an unloader at the end of the line to stack the completed PV cells ready for collection. Setting up a PV cell assembly facility is barely more complex than buying and installing the production line. It can be commissioned as a standard, off the shelf, turnkey installation. A typical modern production line is rated at 1,200 units per hour (UPH), allowing easy synchronisation with other production activities. Predictable performance allows users to scale production easily to achieve the desired overall capacity expressed in megawatts. Screen printing processes such as those that benefit from DEK’s inline production techniques are particularly easily replicated using cost-effective equipment. A number of accelerator technologies are also available to support future speed increases when the industry requires. These include dual-lane printing, for

example, a technique that is already proven in the surface-mount electronic assembly market. Another expected development is to increase the printable area for thin film PV cells to increase total effective throughput. Large-format printing solutions are already available to meet this demand, based on existing technologies developed for manufacturers of large backplane assemblies for telecom switches and Internet servers. Suppliers to the emerging world PV cell production market must demonstrate a robust roadmap capable of delivering throughput in excess of 2,400 UPH going forward. Technical trends Among the important technical trends within PV cell development, manufacturers are using progressively thinner silicon wafers. Typical thickness is being reduced

“PV cell production has been a low volume, niche activity for the majority of its history. The traditional companies supplying capital equipment tend to be organised accordingly. As a result, maintenance, service and process support infrastructures are not normally configured to serve large numbers of customers operating in diverse global areas.” from around 220-200 microns to the region of 180-150 microns. This is partly a response to the general shortage of silicon caused by the rapid ramping of production volumes worldwide. A benefit is that the overall weight of the panel is reduced, making for easier transportation and installation. The thinner wafers are more vulnerable to damage in production, however. Poor handling or clamping mechanisms are major contributors to lost yield through breakage. Enhanced wafer support and automatic vision alignment are required. Another major cause of wafer damage is bending due to thermal expansion. Mismatches in the thermal expansion coefficient (CTE) of materials deposited in the top and bottom sides of the wafer can cause the substrate to bow and crack. So-called ‘low-bow’ techniques designed to address these CTE mismatch hazards will demand improved process control for closer matching between the top- and bottom-side deposits. Changes in the sequence of deposition processes are also expected. New ‘hot-melt’ technology for fabrication of bus bars and current collectors, for example, could replace the conventional print/dry sequence. This process uses a pre-heating stage to allow a liquid-metal deposit to be printed at elevated temperature. The deposit subsequently solidifies through natural cooling. Hot melt is expected to

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Light of the world

eliminate the drying stage and thereby achieve faster throughput. Operational enhancements This rapid growth in global demand for PV cells will also bring logistical challenges for manufacturers. Technical support from equipment suppliers is a key issue. PV cell production has been a low volume, niche activity for the majority of its history. The traditional companies supplying capital equipment tend to be organised accordingly. As a result, maintenance, service and process support infrastructures are not normally configured to serve large numbers of customers operating in diverse global areas. In addition, equipment design, production practices and factory capacity are also now struggling to keep pace with accelerating demand. The key issue is that historically low sales volumes for PV panels have warranted reliance on bespoke equipment, built to special order. With the transition to a highvolume global market, capital equipment suppliers must make use of more modern techniques, including basing machine designs on standardised functional blocks and modular construction techniques to meet customer requirements more quickly and at lower overall cost. Historically, a lead-time of some eight months has been the norm among equipment suppliers. This is set to reduce dramatically, to around 12 weeks and shorter. As an example of how equipment design is changing from the ground up to address the revolution going on in the PV cell market, the DEK PVP1200 stencil printring machine is built around a common control platform shared with DEKâ&#x20AC;&#x2122;s surface-mount and semiconductor-packaging equipment. This allows new customer orders to be fulfilled rapidly and also helps ensure a cost-effective solution. Already some established suppliers to the PV industry are struggling to satisfy their existing customer bases. To succeed in the future, PV cell producers will require the levels of support and attention currently enjoyed by manufacturers of PCs, cellphones, gaming terminals, telecom equipment and other high-volume electronic products.

and continued strong acceleration is expected in markets spanning Asian, American, European and African territories. This represents a tremendous opportunity for suppliers of PV products, including established manufacturers and new market entrants. But many equipment suppliers are not prepared for the increased technical, logistical and customer support demands that this emerging age will impose. For manufacturers seeking a leading position going forward, selecting a technology partner with a credible roadmap and suitable support infrastructure will be critical to achieving success. joint World Conference of:

Conclusion: Forward-looking strategy Solar energy appears to have come of age. Valuable help has come in the form of effective government incentives for consumers, as well as public pressure on businesses to adopt greener energy policies. Sales of PV panels are increasing rapidly,

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Global Solar Technology South East Asia â&#x20AC;&#x201C; Spring 2010 â&#x20AC;&#x201C; 29

Interview

Paul Davis— SEMI Solar power is a heavyweight in the renewable energy category, growing at 40% annually, faster than any other form of electricity generation on the planet! Asia is playing a key role in the development of the global solar energy industry. Many countries in the Asia Pacific region have placed emphasis on the development of renewable sources of energy in order to reduce fossil fuel consumption and dependence on fossil fuel imports despite the recent decline of oil prices. These countries also wish to decrease pollution which results from combustion of fossil fuels and to gain sustainability and self sufficiency in power generation. Global Solar Technology’s regional editor, Debasish Choudhury, recently had an opportunity to talk with Paul Davis, president of SEMI based in Singapore, on the prospects of the photovoltaic market in Asia. GSP: SEMI is traditionally involved with semiconductor manufacturing industry. Of late, SEMI created a special interest group named PV Group, dedicated for serving the photovoltaic/solar manufacturing supply chain. How and why did this transition happen? Without question, the electronics aThe SEMI PV Group was formed to enhance member support in this critically important and high growth area. With technologies and industry structure similar to the semiconductor industry—and with more than 20% of SEMI members currently active in PV, including the

industry’s largest equipment and materials suppliers, SEMI is uniquely positioned to support the PV industry growth through reduced costs, efficient technology transfer, global market development, industry standards, market statistics and other services. Because of the synergies between semiconductor, FPD and PV manufacturing, many of our members have developed technologies for these other segments. In addition, many of our members are diversifying their core business strategies and are adopting PV initiatives. With unprecedented sustained growth forecast

30 – Global Solar Technology South East Asia – Spring 2010

over the next two decades, we are seeing an increasing number of our members move into this space. GSP: The traditional markets for PV— Germany and Spain—are maturing. Which countries do you think offer the future potential for growth of the PV market worldwide? In terms of polysilicon production, the U.S. is the leader, followed by China, Germany and Japan—with Hemlock being the greatest producer in the U.S. But, according to the Yole Development PV TEAM report, Asia is increasing its

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Interview

capacity and is expected to become a leader by 2010. In crystalline silicon cell production capacity, China, Germany and Japan are the top producers. China alone has more than 30 fabs that have a production capacity of over 4 giga watt (GW). However, Korea should be observed closely because of its plasma display manufacturing synergies as demonstrated in most recent news where LG made the decision to convert its A1 plasma panelmanufacturing line in Gumi, Korea, into solar cell production lines. In the thin film market, Germany, the U.S. and Japan are the leaders. Notably, the U.S. lays claim to many emerging technology patent applications and startups, particularly in Silicon Valley and the Pacific North-West. Finally, India will play a significant role in the PV world market as its government has committed to fab city projects, and recent announcements have been made about increasing production in the region. SEMI recently named Sathya Prasad president of the newly formed SEMI India. He is charged with supporting

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SEMI members from all regions that have interests in India’s burgeoning microelectronic and photovoltaic manufacturing supply chains. GSP: What is your estimate on the production and demand of PV in Asia-Pacific by 2010/2012? Apart from China, which are the other countries that will drive the solar PV growth in A-Pac region? Do you think A-Pacific countries have long term vision and strategy for harnessing the solar PV energy? As touched on in the previous question, Asia-Pacific countries to watch in terms of solar production growth over the next few years are Japan, Taiwan, Singapore and Southeast Asia. Subsidies, feed-in tariffs and other legislation in Asia-Pacific countries are beginning to create favourable conditions for PV fabs and adoption at the consumer level as well. These regional markets should continue to see healthy growth contingent upon continued governmental subsidies and other incentives. For more information about the

SEMI PV Group, please read “The Perfect Industry—The Race to Excellence in PV Manufacturing,” which can be downloaded in PDF format from the PV Group’s website at www.pvgroup.org/perfect. The white paper outlines four attributes of the perfect industry: long term growth, sustained profitability, environmental excellence and global scope. Each of these attributes is examined to explain and understand their role in the industry’s formation and to help understand and describe the necessary industry actions required to achieve the greatest impact. Current and potential SEMI policies, programs and initiatives that address each of these attributes are also discussed in the white paper. Thank you, Paul. —Debasish Choudhury.

Global Solar Technology South East Asia – Spring 2010 – 31

Technological Industry Newsdevelopments

Technological developments IMEC’s spray-coating technique holds promise for cheap, fully solutionprocessed organic solar cells IMEC has demonstrated a fully solutionprocessed organic solar cell with a spray-coated active layer and a metal top contact spray-coated on top. The resulting cell shows power conversion efficiencies above 3%, a performance comparable to organic solar cells produced by spin coating of the organic layer and vacuum evaporation of the top contact metal. This is an important step towards producing organic solar cells with cheap and large-area processes. Polymer-based (organic) solar cells hold the promise of low-cost production and a high throughput. However, this can only become true if all the layers of the cells can be deposited by solution-based, in-line compatible methods. IMEC’s research now shows that spray-coating is a suitable

deposition technique, and that it can be used to deposit all layers, including the metal top contact. Spray-coating is a highrate, large-area deposition technique that ensures an ideal coating on a variety of surfaces with different morphologies and topographies. It is frequently used for industrial coating and in-line deposition processes. In spray-coating systems, the ink is atomized at the nozzle by pressure or ultrasound and then directed toward the substrate by a gas. An added advantage of spraycoating is that it is efficient: compared to other techniques only a small amount of the solutions are wasted. IMEC demonstrated that an active layer—a solution of P3HT and PCBM—deposited with spray-coating shows power conversion efficiencies above 3%, a performance which is comparable to that of spin-

UPO scientists increase the efficiency of a type of solar cell by incorporating ionic salts Within the Consolider HOPE project (projects funded by the Ministry of Innovation and Science), a group of scientists at Universidad Pablo de Olavide (UPO), headed by Juan Antonio Anta, are working on the optimisation of a type of photovoltaic cell (Grätzel cell) that artificially mimics photosynthesis. Grätzel cells are photovoltaic devices that take advantage of the interaction of a structured

(a) Schematic build-up of the organic solar cell, (b) SEM and (c) FIB/TEM cross sections of the polymer solar cell with a spray coated Ag top contact.

coated devices. And for the metal top contact, IMEC spraycoated a solution with silver nanoparticles. The challenges are to do this without dissolving the underlying layer, and without damaging it by the temperature needed to sinter the silver nanoparticles. IMEC demonstrated that spray-coating greatly reduces the damage to underlying layers compared to other techniques. It was also able to sinter the silver nanoparticles at 150˚C, a temperature that is compatible with processing on flexible substrates.

semiconductor less than nanometre in size and an organic dye that acts as a solar collector. According to Elena Guillén, member of UPO’s Coloides y Celdas Solares Nanoestructuradas (Nanostructured Colloids and Solar Cells) Group, this dye can be either synthetic or natural and can even enable the use of chlorophyll for this type of cell. Thus, researchers at UPO have begun a study with which they hope to increase the efficiency of these eosin or

32 – Global Solar Technology South East Asia – Spring 2010

Tom Aernouts, teamleader Organic Photovolatics at IMEC, said, “R&D on organic solar cells has entered the stage where we can consider low-cost high-volume manufacturing, which is essential for the uptake of this technology by the industry. Our results show that IMEC has the expertise and knowhow to play an important role in organic photovoltaics R&D.”

mercurochrome -based organic components by incorporating ionic salts, known as green solvents, with a view to preventing evaporation of the liquid compounds and the consequent reduction in efficiency. Previous studies show that ionic salts are less volatile and it is this characteristic that the group headed by Professor Anta seeks to exploit. “Notwithstanding its liquid state, these types of solvents have high viscosity levels and, therefore, during the coming months we will continue our study, working on different alternatives within

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Technological developments

ionic liquids, their synthesis, etc.,” says Elena Guillén. The pros and cons of the new generation Although there are already some third generation cells on the market (for example, for recharging mobile phones), according to the researchers their practical use is anecdotal. However, due to their properties of flexibility and variety of colours and shapes, the future of these cells lies in new market niches such as decoration or use in coloured windows that not only allow light through but use this light to generate electricity. On the other hand, apart from the rapid amortisation of energy production costs -estimated in one year’s use-, there is also the low cost of the materials. “Organic materials are usually cheaper,” affirms the researcher, despite which the search continues for an alternative organic dye to the one currently used, derived from ruthenium. “The paradox lies in the fact that if one uses these cells because their competitive edge is that they are cheaper and more readily available, and then one uses a dye based on a precious metal, what is the advantage?” points out Elena Guillén. On the other hand, the researchers are aware that it is a relatively new technology -this type of cell was invented in 1991that still need to be greatly developed. Furthermore, the maximum efficiency obtained in laboratory is only 11%, which is competitive but it drops when extrapolated to an industrial scale. The main technological challenge is currently the problem of cell degradation. “If you use an organic dye, it can be degraded by the action of sunlight, with the consequent reduction in useful life compared to silicon cells. On the other hand,” the researcher highlights, “our group is working on one of the key aspect for improving cell stability - elimination of the need to use liquids that can present problems with evaporation, etc. and for which, as already mentioned, our focus is on the use of ionic salts.” World record: 13.4% conversion efficiency in solar cells on plastic film A new record efficiency of 13.4% for copper-indium-gallium-diselenide solar cells (CIGS) on a plastic substrate produced on an industrial roll-to-roll system had been recorded by Solarion AG from Leipzig, Germany. The record cells do not employ antireflective coating. The result has been

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independently verified by the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany. “This achievement shows that our proprietary ion beam technology for the production of flexible solar cells not only uses less raw materials and energy, but also reaches high conversion efficiencies,” said Alexander Braun, CTO of Solarion AG. “This result is not only a world record efficiency for flexible CIGS solar cells manufactured on a plastic substrate in an industrial roll-to-roll coating process, but is also the highest efficiency for any thin film solar cell on a flexible polymer substrate from a roll-to-roll process, regardless of the absorber material.” The patented ion beam process for producing the CIGS absorber developed by Solarion AG allows the reduction of process temperature and thus the use of a flexible polymer substrate. “The combination of a low-cost polymer substrate, the ion beam technology and a roll-to-roll production process allows us to reduce manufacturing costs significantly,” said Karsten Otte, CEO of Solarion AG. The flexibility and high efficiency of these solar cells opens up new large-volume applications. For example, such solar modules can be integrated directly into building systems for roofing and facade solutions. Moreover, modules with flexible CIGS solar cells can also be used for standard photovoltaic applications. Ascent Solar achieves 14% cell efficiency milestone in commercial production Ascent Solar Technologies, Inc., a developer of state of the art flexible thin-film solar modules, met a new manufacturing milestone by achieving 14% cell efficiency for its copper, indium, gallium, selenide (CIGS) on flexible plastic substrate produced at its Fab1 (1.5 MW) commercial production plant. U.S. Department of Energy’s National Renewal Energy Laboratory (NREL), the nation’s primary laboratory for renewable energy and energy efficiency research and development, measured 14.01% cell efficiency for Ascent Solar CIGS material. Adding to this news, Ascent Solar announced a peak efficiency of 11.7% for its monolithically integrated CIGS modules manufactured at its Fab1 (1.5 MW) plant in Littleton, CO. Dr. Farhad Mogahadam, President & CEO for Ascent Solar said, “This is a significant breakthrough in demonstrating our ability to achieve thin film CIGS cells with 14% efficiency from regular

production machines. Ascent Solar’s ability to manufacturer monolithically integrated modules with efficiency as high as 11.7% in regular production serves as a vital element to our low cost per watt manufacturing goal.”

Solarmer Energy continues to break world records with 7.6% efficient plastic solar cell Solarmer Energy, Inc., broke the plastic solar cell world record for a second consecutive time. Solarmer announced today their champion plastic solar cell efficiency of 7.6%, certified by the Newport Corporation’s Technology and Applications Center’s Photovoltaic (TACPV) Lab. The Newport Corporation is a globally recognized leader in advanced technology products and solutions. Plastic solar panels, the next generation of solar products, will be flexible, transparent, and able to generate low cost clean energy from the sun. Attractive and colorful, customizable shape and sizes, and better low light performance are just a few in a long list of unique characteristics of plastic solar panels. These solar panels will transform the renewable energy industry, because of their ability to drive cost down to 12-15 cents/kWh and much less than $1/Watt. In the process of completing their pilot manufacturing line, this efficiency milestone increases anticipation for Solarmer’s plastic solar panels, which will be available next year. “Breaking the 7% efficiency barrier for organic photovoltaics is a huge accomplishment for Solarmer and the organic photovoltaic (OPV) industry,” said Dr. Gang Li, vice president of technology development. “We are thankful for the contributions of our two primary collaborators, Prof. Luping Yu at the University of Chicago and Prof. Yang Yang at UCLA. We believe that our world class team will ensure that we continue along the path to the commercial success of OPVs.”

Global Solar Technology South East Asia – Spring 2010 – 33

New Products

New products

Despatch Industries introduces new dual lane UltraFlex firing furnace Based on the unprecedented market adoption of the single lane UltraFlex™ firing furnace and dryer, Despatch Industries has created a high-capacity, dual lane configuration. The company has already sold its first dual lane unit to a European solar cell manufacturer. The dual lane UltraFlex hosts the same revolutionary features as the single lane furnace, but increases processing capacity to 2400-4000 wafers per hour. The high throughput furnace incorporates Despatch’s Microzone™ technology, which enables shaping of unique firing profiles, independent of belt speed. The Microzones™ are configured to create the sharp divisions and tight control necessary to adapt to the industry’s ever-changing pastes and cell architectures. Despatch’s UltraFlex™ presents a smarter, more efficient tool with a smaller footprint and a first-of-its-kind configuration. The company redesigned the airflow system for increased efficiency and developed new, custom lamps that operate at optimal levels and enable maximum absorption of energy into each cell. The efficient UltraFlex™ configuration incorporates a four-meter drying section that provides optimal drying at faster belt speeds. Despatch’s new, patent-pending VOC Thermal Oxidizer is integrated into the dryer and provides virtually maintenance free elimination of VOCs at point-ofgeneration. www.despatch.com

Harting to display Han-Modular® Docking Frame at Renewtech India 2010 show HARTING’s Han-Modular® system now allows “blind” insertion by automatic processes. Thanks to the newly developed docking frame, it is now possible to set up a modular docking connector even without a housing. This allows the modular system to be used in insertion processes that are not hand-guided. With Han-Modular®, users can select and assemble their “customized” connectors themselves. New models are continually being added to the Han-Modular® series so that customer requirements can be optimally met. Now a new Han-Modular® docking frame

has joined the 36 existing modules . The new docking frame makes it possible to implement a modular docking connector without a housing. Such connectors are needed for racks in switch cabinets, for example. The rack cassette is slid into the cabinet. The connector sides can now be guided together “blind” and securely inserted. This is achieved by a floating frame which can move freely in a range of +/- 2 mm. At the same time, very stable leading, centering pins/bushes ensure that the two connector sides are securely connected to each other. Visit HARTING at stall 113, hall A at Renewtech India. www.HARTING.com

34 – Global Solar Technology South East Asia – Spring 2010

SCHOTT unveils adhesive for use in PV and CSP solar arrays, UVLED and glass-to-metal bonding SCHOTT North America unveiled its new Deep UV-200, a one-part thermally activated silicone adhesive well-suited for a variety of applications that require high ultraviolet (UV), visible and near infrared (IR) transmission, including photovoltaic and concentrating solar arrays and UVLED. Deep UV-200 shows excellent UV stability down to 200 nm. Among its many applications, SCHOTT’s innovative, highly UV transmissive silicon adhesive will enable solar array systems to utilize more sunlight and in turn, generate more energy. SCHOTT’s Deep UV-200 has been engineered to have low-gassing, low reactivity to gamma and electron radiation and thermal stability to 220°C. It also bonds well to a wide variety of substrates and has a long shelf life. Application for the Deep UV-200 is performed at 80° to 100°C by spraying, dipping or casting. Curing is performed at 140° to 180°C for 12 to 24 hours, depending on the flexibility desired (elastic or rigid). www.us.schott.com Sixtron Silexium coatings nearly eliminate light induced degradation in monocrystalline solar cells Sixtron Advanced Materials introduced its patent-pending Silexium™ technology, an antireflective passivation coating that nearly eliminates light induced degradation (LID) in solar cells. A well-known issue for solar cell and module manufacturers, LID reduces the efficiency of modules in the field by up to 5% in the first few hours of exposure to the sun, significantly reducing the net energy harvest. Sixtron has demonstrated that solar cells with a Silexium antireflective passivation coating exhibit at least 88% less LID than solar cells with traditional silanebased SiNx coatings. The optimized process flow and reference architecture was developed by Sixtron at their development laboratory in Montreal with resulting cells benchmarked by the University Center for Excellence in Photovoltaics (UCEP) at the Georgia Institute of Technology. With appropriate process optimization,

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Technological developments

solar cells coated with Silexium films deliver net efficiency gains to existing production lines, delivering increased revenue and boosting profit margins for solar cell manufacturers. The precursor for Silexium films is delivered to industry standard plasma enhanced chemical vapor deposition (PECVD) equipment by Sixtron’s SunBox silane-free gas generation system, which was awarded the Cell Award for Best Process Technology for c-Si Solar Cell Manufacturing at the 2009 Intersolar show in Munich, Germany. www.sixtron.com DEK and Heller announce state-ofthe-art drying technology for solar cell metallization DEK Solar and Heller Industries have unveiled the results of a recent collaboration, a pioneering drying system that enhances the state-of-the-art PV3000 metallization line even further. The alliance between the screen printing and thermal technology specialists has enabled a significant breakthrough in solar cell production, incorporating precise thermal control, improved VOC management and reduced power consumption—all on a compact footprint. The new solar cell dryer, the PVD3000,

equipped to handle increased product throughput over a reduced footprint and with reduced maintenance. Heller’s pioneering dryer concept is based on the principles of hot air convection drying, a process which is conducive to precision thermal control at lower drying temperatures. Offering a significant advantage over conventional IR-based dryers, the PVD3000’s drying technology creates improved air exchange within the process chamber which enables the dryer to manage the increased VOC volume associated with raised throughput. In addition, the specialist catalyst incorporated within the process chamber converts the VOCs to simpler compounds such as carbon dioxide and water. An important by-product of the catalyst conversion is heat which, in turn, is used to enhance the drying process and reduce overall power consumption. www.deksolar. com Silicones for photovoltaic and solar applications ACC Silicones, a European manufacturer of specialist silicone elastomers, launched their new PV range of products specifically selected for use in PV and

Mustang Solar introduces Orion series roll-to-roll deposition platform Mustang Solar’s Orion series is a roll to roll deposition platform designed to meet the unique challenges of flexible thin film PV manufacturing processes. Customizable, the Orion Series offers flexible configurations to meet individual process requirements within a standardized proven production tool set. The flexible design makes future upgrades and process changes easy, enabling customers to cost effectively increase cell efficiencies as their process evolves. www.mustangvac.com

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solar applications. These adhesives and encapsulants are compatible with most materials commonly used in the assembly of solar collectors, PV modules and (CPV) concentrator cells. PV5700/ & PV5701 are non-corrosive RTV adhesives with excellent adhesion properties, suitable for frame and junction box sealing and the attaching of control boxes to the rear of panels. PV2300 (Gel) & PV2218 (59º Shore A encapsulant) is for use in CPV units to improve light transmission and provide environmental protection. They are both optically clear, UV stable and nonyellowing. PV2553 thermally conductive potting compound aids the fast and efficient removal of heat from by-pass diodes and electronic circuitry whilst also providing environmental protection for sensitive components. PV2430 has been tested and approved to meet UL 94 V-0 for electrical potting. Flexible manufacturing facilities also enable ACC Silicones to offer bespoke products for specific applications when required, subject to commercial evaluation. www.acc-silicones.com

New hydrophilic PTFE filters from Gore for high-purity chemical processing W. L. Gore & Associates (Gore) has added hydrophilic PTFE filters to its expanding line of cartridge filters for bulk high-purity chemicals used in microelectronics and photovoltaic manufacturing. GORE® Filters for High-Purity Chemical Processors can be used as drop-in replacements

Global Solar Technology South East Asia – Spring 2010 – 35

Solar PV systems market in Southeast Asia to reach US $255 million by 2016

Solar PV systems market in Southeast Asia to reach US $255 million by 2016 The on-going global struggle to reduce emissions necessitates large-scale adoption of solar PV systems in Southeast Asia, forecasts a new Frost & Sullivan analysis. Traditionally in Southeast Asia, solar energy has been predominantly used for heating water and drying purposes and seldom for generating power. However, penetration of solar photovoltaic (PV) systems has been growing across the region over the last ten years, where it is used for electrifying rural and remote homes and villages. Solar photovoltaic (PV) systems provide the ideal environment friendly power generating solution for electrifying remote rural areas in power deficient areas of Southeast Asia as it is neither technically nor economically viable to extend grid coverage to certain isolated areas. In addition, urban end-users’ growing preference towards adopting sustainable energy solutions has accelerated the adoption of solar PV systems, particularly for roof-tops and buildings. Furthermore, strong government support through policies, feed-in-tariff schemes and other deployment programs have resulted in Chart 1. Total solar PV systems market: installed capacity (Southeast Asia), 2009.

gradual uptake of solar PV systems both for on-grid and off-grid application. The new analysis from Frost & Sullivan, titled “Southeast Asian Solar PV Systems Market Outlook”, finds that the solar PV systems market earned revenues of $99.6 million in 2009 and estimates this to reach $254.8 million in 2016 due to increasing awareness about environment friendly power generating technologies, global decline in prices, strong government support for renewable energy and use of solar power for rural electrification purposes. “Favorable topography with adequate solar radiation throughout the year coupled with policies and regulations from the government are likely to expand market opportunities during the next five to seven years Southeast Asia especially in countries such as Thailand, Malaysia, and the Philippines,” says Frost & Sullivan Program Manager Suchitra Sriram. “The introduction of feed in tariff is expected to be a big stimulant for on-grid solar PV system installations for both distributed and centralized solar power plants.” Market trends indicate burgeoning Chart 2. Total solar PV systems market: installed capacity (Southeast Asia), 2016.

Installed Capacity = 72.39 MWp

demand owing to strong governmental commitment to the promotion of solar energy and creation of sustainable cities. However, market penetration of solar PV systems has been challenged by the high cost of installation as the majority of customers fall under the low-income group. Thus, market growth is heavily dependant on government support in terms of policy guidelines, tax credits, subsidies or rebates, until the price reaches grid parity. Moreover, the well developed power infrastructure deters the use of solar PV systems in some urban areas. The global financial crisis did not have a major impact on the solar PV systems market in Southeast Asia. However, due to the ripple effects of the financial crisis on the key global solar power markets, the economic viability of some PV projects diminished because of lack of credit from banks, financial agencies and donor countries. Another factor that contributed to restrained market momentum was the extensive use of diesel fired generator sets and other low-cost renewable energy technologies. To rev up the pace of growth of the Chart 3. Total solar PV systems market: revenue forecasts (Southeast Asia), 2009-2010. 280

Installed Capacity = 189.82 MWp

Malaysia 14.2%

Indonesia 21.8%

Rest of Southeast Asia 1.2%

Malaysia 24.8% Rest of Southeast Asia 1.1%

Singapore 3.7%

Indonesia 18.1%

The Philippines 8.8% Vietnam 1.1%

36 – Global Solar Technology South East Asia – Spring 2010

Revenues ($ Million)

240 Singapore 1.5%

200 160 120 80 40 0

The Philippines 8.8%

2009

2016

Note: All figures are rounded; the base year is 2009. Source: Frost & Sullivan

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Solar PV systems market in Southeast Asia to reach US $255 million by 2016

solar PV systems market in the Asia Pacific region, it is vital for countries to establish realistic targets, streamline the policy framework, and aggressively boost customer awareness. Going forward, as production costs decline and solar PV systems gain traction, installation costs are expected to reduce and pave the way for large-scale commercialization. This, in turn, will attract new entrants across the solar industry value chain. Currently, the systems market is highly fragmented and competitive in nature with more than 85 companies present in the solar industry value chain. Well-known multinational companies whose solar PV modules and panels are popular in Southeast Asia include SHARP CORPORATION, KYOCERA Corporation, Mitsubishi Electric Corporation, SolarWorld AG, Renewable Energy Corporation ASA, SIEMENS AG, BP Solar International Inc., and so on. Besides, Chinese modules are penetrating the market. While some of the multinational companies also undertake system integration and installation, the market is cluttered by regional and local companies such as GRENZONE Pte Ltd., Phoenix Solar Pte. Ltd., Solamas Sdn. Bhd., Intelligent Power Systems Technology, Annex Power Co., Ltd., and so on. Growing demand, coupled with attractive profit margins is likely to entice new entrants into this market. “Considering the highly competitive nature of the market, it is imperative for system integration companies to focus on enhancing growth by establishing a strong technical workforce and providing high-quality PV components,” says Sriram. “Also, participants must ensure on-time delivery of products and provide superior value-added maintenance services to outpace competition.”

Frost & Sullivan, the Growth Partnership Company, enables clients to accelerate growth and achieve best-in-class positions in growth, innovation and leadership. The company’s Growth Partnership Service provides the CEO and the CEO’s Growth Team with disciplined research and best-practice models to drive the generation, evaluation, and implementation of powerful growth strategies. Southeast Asian Solar PV Systems Market Outlook is part of the Energy & Power Growth Partnership Service program.

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New Products— continued from page 35

for existing filters to achieve significant flow improvements while maintaining or increasing particle retention. This dramatically increased performance can provide a retention upgrade while maintaining system flow, reducing processing time, or decreasing the number of filters required for a lower total cost of ownership. The new filters incorporate Gore’s proprietary high-flow hydrophilic PTFE (polytetrafluoroethylene) filtration media, which does not require IPA (isopropyl alcohol) pre-wetting and completely eliminates de-wetting issues in most applications. They are well suited to filtration of aqueous and high-surfacetension liquids, especially where outgassing or bubbles are a concern. Applications include high-throughput filling, packaging and recirculation systems. www.gore.com/ filters RASIRC introduces the Steamer ‘02 for ultrapure process steam RASIRC®, the steam purification company, introduces the RASIRC Steamer ‘02, the next generation in ultrapure steam generation and control. The RASIRC Steamer is the only technology to generate purified steam from de-ionized (DI) water. Users of the RASIRC Steamer obtained improved oxide growth rate, film quality, and reduced operating costs. The Steamer can be used in the semiconductor, MEMS, solar, and optical device industries where thermal oxide films are an essential feature. RASIRC’s new steamer introduces additional control loop for the heated steam process line between the steamer and the tool as well as an integrated flow meter for improved repeatability, flow accuracy, and response time. The system also offers reduced footprint and simplified installation through the addition of an internal three-way valve, and improved tracking of flow rate and energy use through an updated user interface. Compared to pyrolytic torches, there is no thermal build up with increased flow rate, it’s safer as hydrogen and oxygen are eliminated from the oxidation process, it operates at significantly lower temperature, and handles a wide range of pressures and flow rates. www.rasirc.com

BrightView unveils in-line process control and otimization tool for thin-film cell manufacturing BrightView Systems unveiled the InSight M series, the world’s first in-line process control and optimization tool developed specifically to address the challenges faced by thin-film solar cell manufacturers. The wide area metrology (WAM) system provides continuous monitoring and whole-panel mapping of critical material and process parameters at full production throughput and for 100% of manufactured panels. Easily integrated at key steps in any thin-film production line including single-junction and multi-junction silicon, the system allows panel producers to implement process optimization solutions that enhance average panel efficiency, improve line productivity and verify full compliance with the strictest durability and quality requirements. The system architecture allows for easy integration into the design of new production lines or insertion into existing ones, including Gen 5 and Gen 8.5 lines. With its innovative True Cell™ technology, the InSight is able to measure and map critical layers on-the-fly within the actual product stack, providing continuous process fingerprinting that drives production improvement, excursion detection and line productivity. The InSight M series represents a systems approach to enhancing thin-film production. www.brightview-sys.com

Global Solar Technology South East Asia – Spring 2010 – 37

Title Industry News

Industry News

Events Calendar 9-11 March 2010 Renewtech India 2010 Pune, India www.renewtechindia.com

5-7 May 2010 SNEC PV Shanghai, China www.snec.org.cn

28-30 July 2010 SOLARCON India Hyderabad, India www.solarconindia.org

22-23 March 2010 Solar Business Bangkok 2010 Bangkok, Thailand www.solarbangkok2010.com

9-11 June 2010 Solar Taiwan 2010 Taipei, Taiwan www.optotaiwan.com

27-29 October 2010 DIREC 2010 New Delhi, India direc2010.gov.in

21-23 April 2010 Renewable Energy World @ PowerGun India 2010 Expo Mumbai, India www.power-genindia.com

30 June-2 July 2010 PV Japan 2010 Yokohama, Japan www.semi.org/PVJAPAN-EN

38 – Global Solar Technology South East Asia – Spring 2010

www.globalsolartechnology.com

Title

The billion dollar question

Mr K Subramanya CEO, Tata BP Solar

The billion dollar question Now that finally the long awaited National Solar Mission has been announced, India should be able to start using solar power in a significant way and make a mark for itself in the global solar energy industry. The solar mission lays out an ambitious vision and a broad framework to make India a world power in the use of solar energy, and it fixes an ambitious target of generating 20,000 MW of solar power by 2022. From the current installed solar power base of less than 200 MW, this would mean growing the Indian market 100 times over the next 12 years! The billion dollar question is: can we do it? The answer is not easy. True, the country is richly endowed with sunshine. From Kashmir to Kanyakumari and from Kutch to Kohima, if there is one natural resource that is commonly available all over India, it is the sun! We have on average 300 days of sunshine, and the average solar radiation varies from 4 to 7 kWh/ m2 per day. The total sunshine falling over India is more than 5000 trillion kWh! If we could use just a fraction of it to convert it into sunlight, we could solve our energy needs! However, the fact is that we have not been able to develop a solar energy industry of any significant scale so far. Even though India is currently facing a huge shortage of energy, we have not paid as much attention as needed towards renewable sources of energy, solar in particular. At present, we have a 12% gap between demand and supply of electricity and it peaks to 16-17%. This is at a time when roughly half of the billionplus population does not have access to basic lifeline electricity. The per capita consumption of India is one-fourth of the global average. The Indian government has laid out an ambitious target of supplying Power to All by 2012. Further the target is to supply 1000 units of electricity per capita by 2012. By present estimates, we are going to miss this target! On the other hand, there are at least

105,000 villages out of a total of 600,000 villages that are not yet officially electrified. A large number of these villages are either located in remote and difficult locations or are sparsely populated and it is not technically feasible or economically viable to extend the electricity grid there. Solar power can be used to provide electricity to all these remote locations and transform the lives of the people in a very short span of time. So the question—whether India can achieve the targets under the solar mission—needs to be answered in the affirmative. Yes, we can achieve the targets if the mission receives the political leadership and policy direction that it deserves along with the required budgetary support to enable the solar industry to grow to a minimal critical mass. The immediate challenge is to reach the target of 1000 MW of grid-connected and 200 MW of off-grid installations, which has been set out for the first phase up to March 2013. If we can achieve these targets adequately and in time, it will set off a positive energy for the rest of the targets to follow. The solar mission strategy to appoint the NTPC Vidyut Vyapar Nigam (NVVN) as the nodal agency that will be charged with the task of purchasing solar power from developers and selling to State utilities, along with equivalent amount of thermal power from the unallocated quota of NTPC stations, should hopefully work well. Unlike its parent, NVVN is a new entity and its performance will be watched keenly as the success of the framework will depend on its ability to sign power sale agreements with state transmission utilities and accordingly to sign power purchase agreements with solar power developers. The state utilities will be required to purchase 0.25% of their total purchase from solar power producers and this portion will eventually rise to 3% by 2022. This RPO will open an assured market for

40 – Global Solar Technology South East Asia – Spring 2010

solar power producers. The CERC had issued the generic tariff for renewable energy in its order on 03 December 2009 at Rs. 18.44 per kWh for solar PV projects in case accelerated depreciation is not availed of and Rs. 17.14 per unit in case accelerated depreciation is availed of by the power developer. Besides the generic tariff, the CERC regulations also provide for project specific tariff which a developer can decide to pursue. However, while the industry was absorbing this news it started realizing that this tariff was only for projects commissioned before 31 March 2010. At present, not a single project will benefit from this tariff, as far as we know, and the figure of 18.44 will remain of academic interest only. The tariff to be applied for projects starting in 2010-11 will be based on newly announced normative capital cost of Rs. 15.2 crore/ MW (down from Rs. 17 crore/MW used in the 03 Dec 2009 notification). At a public hearing organized by the CERC on 10 February, solar power developers and manufacturers argued and pleaded with the CERC not to reduce the normative capital cost figures. At the time of writing the new notification from CERC on the normative capital cost for solar power project in 2010-11 and the generic tariff for the same is awaited. Mr Subramanya has been associated with Tata BP Solar since its inception. He was appointed chief executive officer of the company in 2006.

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