Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
Morphological Investigation of Small Molecule Solution Processed Polymer Solar Cells Based on Spin Coating Technique1 Liyakath Reshma 1, Kannappan Santhakumar 2,a 1 – School of Electronics Engineering, VIT University, Vellore, Tamil Nadu, India 2 – Carbon Dioxide and Green Technologies Centre, VIT University, Vellore, Tamil Nadu, India a – ksanthakumar@vit.ac.in DOI 10.2412/mmse.42.77.422 provided by Seo4U.link
Keywords: polymer solar cell, small molecule, bulk heterojunction, spin coating, power conversion efficiency.
ABSTRACT. Organic solar cells are one of the best candidates to overcome the traditional energy depletion and energy pollution, because they use simple processing techniques to fabricate and they are under intense investigation in academic and industrial laboratories because of their potential to enable mass production of flexible and cost effective devices. Here we explore an efficient solution-processed polymer bulk heterojunction solar cells based on the combination of a small molecular donor ((DTS(PTTh2)2) and an acceptor (PC71BM ) by using chlorobenzene as a solvent in order to obtain the mixing morphology through spin coating. PEDOT: PSS was used as a surface modifier to reduce the work function of the conductors. The molecular aggregations in chlorobenzene solvent were investigated by means of UV–visible spectra and photoluminescence measurements. The surface morphology of the active layers deposited was examined using atomic force microscopy. The current density–voltage (J–V) characteristics of the photovoltaic cells were measured under the illumination by using Oriel 1000W solar simulator and the maximum power conversion efficiency has been reported for this polymer combination. These results indicate that the spin coating technique can be a viable alternative to the highcost and vacuum-deposited ITO for mass production and low cost roll-to-roll based solar cells.
Introduction. The world’s demand for usable energy increases every year, with an expected increase from 479 trillion joule (505 quadrillion Btu) in 2008 to 730 trillion joule (770 quadrillion Btu) in 2035, an increase of 52 %. In order to meet this demand, non-renewable fossil fuels, mostly coal, and renewable sources of useful energy will need to be deployed. As fossil fuels will eventually run out and their use seems to be as the main contributor to the increase of the global greenhouse effect, more research done on the development and deployment of alternative technologies for renewable energy production. Sunlight is an abundant and virtually eternally renewable energy source, with 174 petawatt of power arriving at the earth’s atmosphere and about 89 petawatt is absorbed by land and water. Even using only a fraction of this enormous amount of power may significantly meet the world’s growing demand for power. Solar cells, which rely on the photovoltaic effect, transform sunlight into electricity and in order to successfully utilize solar power, developing well performing and cost-effective photovoltaic devices is paramount. Solar cells can be categorized into two different kinds, inorganic and organic ones. The former having current commercial power efficiency between 15 and 20 %, up to 25 % for more refined silicon cells and top lab-scale efficiencies of more than 40 % reached with lab-scale multi-junction devices consisting of various inorganic semiconductors and the usage of light concentration techniques. However, the performance of organic solar cells (or Organic Photovoltaic’s OPV's) is considerably lower with a commercial efficiency of about 3 to 5 % and a current top efficiency of 1 0 . 6 %. Organic electrondonor/electron-acceptor blends are a key ingredient of “plastic” photovoltaic devices, whose development raises an ever-increasing scientific interest due to their low cost, easy production process and mechanical flexibility. Thus, OPV research has taken a new direction in exploring the uses of 1
© 2017 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/
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