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IntegratedCircuitsandSystems SeriesEditor
AnanthaP.Chandrakasan
Forfurthervolumes: http://www.springer.com/series/7236
EugenioCantatore Editor
ApplicationsofOrganic andPrintedElectronics ATechnology-EnabledRevolution
Editor
EugenioCantatore DepartmentofElectricalEngineering EindhovenUniversityofTechnology Eindhoven Netherlands
ISSN1558-9412
ISBN978-1-4614-3159-6ISBN978-1-4614-3160-2(eBook) DOI10.1007/978-1-4614-3160-2
SpringerBostonHeidelbergNewYorkDordrechtLondon
LibraryofCongressControlNumber:2012944381
SpringerScience+BusinessMediaNewYork2013
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Preface TheDisruptivePotentialofLow-Cost, Low-TemperatureTechnologiesforElectronics Electronics,andmorespecificallyintegratedcircuits(IC),havedramatically changedourlivesandthewayweinteractwiththeworld.Followingtheso-called Moore’slaw[1],ICcomplexityisgrowingexponentiallysince40years,andthis trendispredictedtocontinueatleastforthecoming15years[2].Theabundanceof electronicfunctionsataffordablecosthasenabledawealthofapplicationswhere themainICstrengths,namelycomputationalspeedandmemorycapacity,arewell exploited:PCs,portabledevices,gameconsoles,smartphonesandalike.The commercialsuccessofintegratedelectronicsisbasedonasymbioticdevelopment oftechnologyandapplications,wheretechnicalprogressandeconomicgrowth nurtureeachother.Thisprocessrequireslotsoftimeandeffort:firstICpatents wherefiledin1949[3],butitisonlyin1971thatthefirstcommerciallyavailable microprocessor(Intel4004),oneofthemostfar-reachingapplicationofICs,gained themarket;andPCsbecamepopularonlyinthesecondhalfoftheeighties.
Themainstrengthofintegratedelectronicsisinthelow-cost-per-function enabledbyanevergrowingminiaturization:mono-crystallinesiliconrealestateis veryexpensive,butthenumberoftransistorsthatcanbeintegratedperareagrows accordingtoMoore’slaw,bringingdownthecosttorealizeagivenfunction.
Sincethesecondhalfoftheseventies,acompletelydifferentelectronicparadigm,theso-calledlarge-areaelectronics,hasbeendeveloping.Inthisfieldthe majoraimistodecreasethecostperarea(insteadofthecostperfunction), enablinglargesurfacescoveredwithelectronicdevices.Themainapplicationof thiskindoftechnology,typicallybasedonamorphousorpolycrystallinesilicon transistors,isinactive-matrixaddressingofflatdisplays.Thesuccessofthis technologyhasbecomeevidentinthelastdecade,whenflat-panelLCDdisplays haveswiftlyreplacedtraditionalcathoderaytubesintelevisionsets.
Amorphousandpolycrystallinesilicontechnologytypicallyrequirehigh-temperaturevacuum-basedprocessing,withtheconsequencethatglasssubstratesare
usedandthatthetechnologythroughputislimited.Intheninetiesanewtechnology approachhasbeenproposed,basedonmaterialsthatenablelow-temperatureprocessingandtheuseofveryhighthroughputpatterningtechnologies,borrowedfrom thegraphicprintingfield:organicandprintedelectronicswereborn.
Theword‘‘organicelectronics’’,whichIpersonallystartedusingin2000[4] togetherwithmanycolleagues,designateselectronicsmanufacturedusingfunctionalcarbon-basedmaterials,typicallysemiconductors,likepentacene,P3HT, PCBM,PTAAandmanyothers.Thereareseveralreasonsforthischoice:
• Organicmaterialscanformfunctionalfilmswhenprocessedfromsolutions, pavingthewaytomanufacturingprocesseswithareducednumberofvacuum steps(whicharetypicallyexpensiveandcumbersometoscaletolargeareas), andthusenablingpotentiallyverylow-costlarge-areaelectronics;
• Organicmaterialsareprocessedatlowtemperature(typicallybelow200 C), enablingtheuseofinexpensiveandflexibleplasticfoilsassubstratesandpaving thewaytoflexibleelectronics;
• Organicchemistryisintrinsicallyveryrich,enablingtheexplorationofalimitlesslibraryofmaterialshavingverydiverseelectrical,optical,rheologicaland chemicalproperties;
• Togetherwiththechemicalvariety,alargespectrumofphysicallydifferent devicesbasedonorganicmaterialsispossibleandhasbeendevelopedinthe years,themostwell-knownbeingorganiclightemittingdiodes(OLEDs)[5], organicthin-filmtransistors(OTFTs)[6,7],organicphotovoltaics(OPVs)[8], organicsensors[9],organicmemories[10,11],andorganicMEMs[12]1.
Togetherwiththesestrengths,functionalorganicmaterialsandorganicelectronicspresentanumberofdrawbacks:
• Organicsemiconductorshavearelativelypoormobility,withpeakvaluesfor single-crystalmaterialsintherangeof10cm2/Vs[13],andtypicalvaluesin solution-processedfilmsofabout1cm2/Vsatthestateoftheart.Underthis pointofview,othermaterialssuitableforlow-temperatureandlarge-areaprocessing,likemetal-oxidesemiconductorsandcarbonnanotubes,mayofferan advantagecomparedtoorganicsemiconductors.
• Organicsemiconductors(especiallyn-type)aresensitivetooxygen,moisture andotherenvironmentalaggressors,sothatforlongtimeorganicelectronic deviceshavehadpoorshelfandoperationallifetime.Organicmaterialsarealso sensitivetobiasstress,whichtendstoaffectoperationallifetime.Recent improvementsinthematerials,theirformulationandencapsulation,however, showthatinstabilitiesshouldnotbeashow-stopperforcommercialization(see forinstance Sect.2.3 in Chap.2 and Sect.4.4 in Chap.4);
1 Inthissectionafewearlyandsignificantpapershavebeenselectedasreferences.
•
Organicsemiconductorsaredifficulttodopeinsituwithhighlycontrolled dopantconcentrationsasaprocessequivalentoftheionimplantationdoping usedinsiliconhasstillnotbeendevelopedfororganicmaterials.Thismakes difficulttomanagekeyparametersliketransistorthresholdvoltagesandinjectionbarriersatthecontacts.
Manymoredetailsonthestateoftheartandroadmapsoforganicelectronics aregivenin Chap.1 andintheotherchaptersofthisbook.
Thecapabilitytodepositorganicmaterialsfromsolutionmakespossibleto patternfunctionalmaterialsusingmethodsadaptedfromgraphicprinting,like inkjet,gravure,slotcoatingandmanyothers.Thisleadstotheconceptof‘‘printed electronics’’.Themainstrengthofthisapproachisthehighthroughputthat characterizesprintingproductionprocesses,whichmeansthatprintinghasthe potentialtomakepossibleveryinexpensivelarge-areaelectronics,andthusto enableapplicationsofelectronicsunthinkabletillnow.Moreover,printingisan additiveprocess,thusonlythefunctionalmaterialsthatareneededareeffectively used,contrarytothetraditionallithography-basedsubtractiveapproach.Thishas thepotentialtodecreasematerialusageandthusfurtherbringdownthecosts. Detailedinformationonprintingelectronicsisavailableespeciallyin Chaps.1, 2 and 6 ofthisbook.
Thestrengthsofprintingarepairedwiththechallengesthatthistechnology faces:itisnamelydifficultandexpensivetodevelopanewelectronictechnology usinganapproachthatinafewminutescangeneraterollscoveredwithhundreds ofmetersofelectronicstobecharacterizedandoptimized.Uniformity,performanceandyieldaredauntingtaskstobesolvedforfutureprintedelectronics applications.
Thepotentiallowcost,thecompatibilitywithlargeflexiblesubstratesandthe wealthofdevicesthatcharacterizeorganicandprintedelectronicswillmake possibleapplicationsthatgofarbeyondthewell-knowndisplaysmadewith conventionallarge-areasiliconelectronics.Organicandprintedelectronicscan enableatruerevolutionintheapplicationsofelectronics:thisistheviewthat broughtme,togetherwithalargenumberofcolleagues,towritethisbook.The volumeofferstothereaderanextensiveoverviewofthedifferentdevicesenabled byorganicelectronics,andreviewsalargevarietyofapplicationsthatare developingandcanbeforeseenforthefuture.
Chapter1,writtenbyTampereUniversity,theOrganicElectronicAssociation (OA-E)andPolyIC,offersacomplete RoadmapforOrganicandPrintedElectronics spanningtilltheendofthisdecade.Itisanidealstartingpointtounderstandthecomplexapplicationscenariosandthelikelydevelopmentsinthisrapidly growingtechnologydomain.
In Chap.2 byKonarka,CyprusUniversityofTechnologyandFriedrichAlexander-University,arediscussed OrganicPhotovoltaics,withgreatemphasis ontheuseofprintingprocessesfortheirmanufacturing.Awideoverviewofthe printingprocessesfororganicelectronicsisgiven,togetherwiththestateoftheart oftheirapplicationtosolarcells.Photovoltaiccellsdonotneedfinepatterningof
thestructuresintheplaneofthedevice,andarethusanidealcandidatetoexploit thehighthroughputofprintingprocesses.Thischapterisanexcellentreading forthepersonwillingtounderstandmoreaboutprintingelectronics.Aroadmap fororganicsolarcellsconcludesthiscontribution.
Inthethirdandfourthchapterlightemittingdiodes(OLED),themostadvanced organicelectronicdevicesavailableatthemoment,arediscussed. Chapter3, writtenbyKyungHeeUniversityandSamsung,givesadetailedoverviewof OLEDDisplays,aboomingapplicationthathasreachedthemarketsincesome yearsalready,andisrapidlygrowingtobecomethestandardemissivetechnology forflatdisplays.ThissectioninformsthereaderaboutthedifferenttypesofOLED pixelsincommercialuseandindevelopment,andgivesinsightintothemost relevantdisplayandbackplaneissues.
Chapter4,byPhilips,givesaniceoverviewof OLEDforLighting applications. Thesectionbeginswithaninsightfuldescriptionofthematerials,physics, architectureandbenchmarkingofOLEDlightingdevices,tocontinuewithan overviewoffabricationmethods,reliabilityandcommercialapplications.
Chapter5 byUniversityofTokyogivesaninterestingvisionforfutureorganic electronics:itwillcomplementsiliconICstocreatenewapplicationsenabling unprecedentedwaysofinteractionbetweenelectronicsandpeople.Inthisvision areincludedavarietyofdifferentorganicdevices(TFTs,sensorsandactuators) providingastimulatingviewonhowdifferenttypesoforganicelectronicscanbe integratedtoenablerevolutionaryapplications.
ThesixthandseventhchapterdealwithorganicTFTs. Chapter6 focuseson applicationsof PrintedOrganicTFTs.Thissection,writtenbyPolyIC,describes thedevicesandtechnologyneededtoprinttransistorsandcircuits,thecharacteristicsofprintedTFTs,andwhatthisrevolutionarytechnologycanmeanin termsofapplications(RFIDsandSmartObjects). Chapter7 byIMEC,KUL, KHL,TNOandPolymerVisionfocusesontheapplicationof OrganicTFTs to low-cost RFIDs.ThissectionexplainshoworganicRFIDsaredevelopingtowards becomingfully-complianttoexistingstandardsforRFIDsbasedonsiliconIC technology.Compatibilitywithstandardswouldmeanthatthesameinfrastructure canbesharedbetweensiliconandorganicRFIDs,enablingaseamlesstransition betweenthetwotechnologiesandaneasymarketuptake.Thisdoesnotmean, however,thatsiliconandorganicshouldservethesamemarkets:thecharacteristicsofprintedelectronicslendthemselvesnaturallytothedreamofenabling item-levelidentificationofretailitems,whichisstilloutofreachforsilicon RFIDs,duetothehighcostsandcumbersomeintegrationofsiliconICswiththe itemstobeidentified.
Chapter8,contributedbyUniversityofCaliforniaBerkeley,reviewsthestate oftheartof ChemicalSensors basedonorganicelectronicdevicesanddemonstratesthespecificcompetitiveadvantagethatthesesensorshave,namelytheease ofcreatingmatricesofsensingelementswithdifferentsensitivitytodiverse analytes,thusenablingtheextractionofuniqueanalytesignaturesandgreatly improvingbothspecificityandversatilityofuse.
Thisbookcanbereadatdifferentlevelsofinsightbybeginnersaswellasby expertsinthefield,andisspecificallyconceivedtoaddressawiderangeofpeople withtechnicalandscientificbackground.Iamdeeplygratefultoallcontributors:I hopeyouwillappreciatetheireffortandIwishyouapleasantandfruitfulreading.
Eindhoven,TheNetherlands,January2012EugenioCantatore
References 1.MooreGE(2003)Noexponentialisforever:but‘‘forever’’canbedelayed!In: ISSCC2003digestoftechnicalpapers,pp20–23
2.ITRSRoadmap(2011)Availableat http://www.itrs.net/Links/2011ITRS/ Home2011.htm
3.JacobiW(1949)Halbleiterverstärker,PatentDE833366,15April1949
4.CantatoreE(2001)Stateoftheartelectronicdevicesbasedonorganicmaterials. In:Proceedingsofthe31stEuropeansolid-statedeviceresearchconference (ESSDERC),pp25–34
5.TangCW,VanSlykeSA(1987)Organicelectroluminescentdiodes.Appl PhysLett51:913
6.KoezukaH,TsumuraA,AndoT(1987)Field-effecttransistorwithpolythiophenethinfilm.SynthMet18:699–704
7.BrownAR,PompA,HartCM,deLeeuwDM(1995)Logicgatesmadefrom polymertransistorsandtheiruseinringoscillators.Science270(5238): 972–974
8.SariciftciNS,SmilowitzL,HeegerAJ,WudlF(1992)Photoinducedelectrontransferfromaconductingpolymertobuckminsterfullerene.Science 258(5087):1474–1476
9.TorsiL,DodabalapurA,SabbatiniL,ZamboninPG(2000)Multi-parameter gassensorsbasedonorganicthin-film-transistors.SensActuatorsB67:312
10.ReedMA,ChenJ,RawlettAM,PriceDW,TourJM(2001)Molecular randomaccessmemorycell.AppPhysLett78(23):3735–3737
11.OuyangJY,ChuCW,SzmandaCR,MaLP,YangY(2004)Programmable polymerthinfilmandnon-volatilememorydevice.NatMater3(12):918–922
12.SekitaniT,TakamiyaM,NoguchiY,NakanoS,KatoY,HizuK,KawaguchiH, SakuraiT,SomeyaT(2006)Alarge-areaflexiblewirelesspowertransmission sheetusingprintedplasticMEMSswitchesandorganicfield-effecttransistors. In:IEEEint.electrondevicesmeeting(IEDM),pp287–290
13.JurchescuOD,PopinciucM,vanWeesBJ,PalstraTTM(2007)Interfacecontrolled,high-mobilityorganictransistors.AdvMater19:688–692
1OE-ARoadmapforOrganicandPrintedElectronics ..........1 DonaldLupo,WolfgangClemens,SvenBreitungandKlausHecker
2Solution-ProcessedOrganicPhotovoltaics ...................27 ClaudiaN.Hoth,PavelSchilinsky,SteliosA.Choulis, SrinivasanBalasubramanianandChristophJ.Brabec
3High-PerformanceOrganicLight-EmittingDiodeDisplays ......57 JangHyukKwon,RamchandraPode,HyeDongKim andHoKyoonChung
4HighEfficiencyOLEDsforLightingApplications .............83 CoenVerschuren,VolkervanElsbergenandReinderCoehoorn
5LargeAreaElectronicswithOrganicTransistors .............101 MakotoTakamiya,TsuyoshiSekitani,KoichiIshida, TakaoSomeyaandTakayasuSakurai
6PrintedRFIDandSmartObjectsforNewHigh VolumeApplications ..................................115 WolfgangClemens,JürgenKrummandRobertBlache
7OrganicRFIDTags ...................................133 KrisMyny,SoerenSteudel,PeterVicca,SteveSmout, MoniqueJ.Beenhakkers,NickA.J.M.vanAerle,FrançoisFurthner, BasvanderPutten,AshutoshK.Tripathi,GerwinH.Gelinck, JanGenoe,WimDehaeneandPaulHeremans
8PrintedOrganicChemicalSensorsandSensorSystems
VivekSubramanian,JosephineChangandFrankLiao
Chapter1 OE-ARoadmapforOrganic andPrintedElectronics DonaldLupo,WolfgangClemens,SvenBreitung andKlausHecker
Abstract Theroadmapfororganicandprintedelectronicsisakeyactivityofthe OE-A,theindustrialorganisationfortheyoungorganic,printedandlargearea electronicsindustry.Organicelectronicsisaplatformtechnologythatenables multipleapplications,whichvarywidelyintheirspecifications.Sincethetechnologyisstillinitsearlystage—andisinthetransitionfromlab-scaleandprototypeactivitiestoproduction—itisimportanttodevelopacommonopinionabout whatkindofproducts,processesandmaterialswillbeavailableandwhen.This chapterisbasedonthethirdversionoftheOE-ARoadmapfororganicandprinted electronics,developedasajointactivitybykeyteamsofexpertsin9applications and3technologyareas,informedbyfurtherdiscussionswithotherOE-Amembers duringassociationmeetings.Theresultingroadmapisasynthesisoftheseresults representingcommonperspectivesofthedifferentOE-Aforums.Throughcomparisonofexpectedproductneedsintheapplicationareaswiththeexpected technologydevelopmentpaths,potentialroadblocksor‘‘redbrickwalls’’suchas resolution,registrationandcomplementarycircuitryareidentified.
D.Lupo(&)
DepartmentofElectronics,TampereUniversityofTechnology, POBox692,33101Tampere,Finland
e-mail:donald.lupo@tut.fi
W.Clemens
PolyICGmbHandCo.KG,Tucherstrasse.2,90763Fürth,Germany e-mail:wolfgang.clemens@polyic.com
S.Breitung K.Hecker
OE-A(OrganicElectronicsAssociation),c/oVDMA,LyonerStreet18, 60538FrankfurtamMain,Germany e-mail:sven.breitung@vdma.org
K.Hecker
e-mail:klaus.hecker@vdma.org
E.Cantatore(ed.), ApplicationsofOrganicandPrintedElectronics, IntegratedCircuitsandSystems,DOI:10.1007/978-1-4614-3160-2_1, SpringerScience+BusinessMediaNewYork2013
Keywords Organicelectronics Printedelectronics RoadmapOE-Aapplications Redbrickwalls Organicelectronicsassociation
1.1Introduction
Organicandprintedelectronicsisbasedonthecombinationofnewmaterialsand cost-effective,largeareaproductionprocessesthatopenupnewfieldsofapplication.Thinness,lightweight,flexibilityandenvironmentalsustainabilityarekey advantagesoforganicelectronics.Organicelectronicsalsoenablesawiderangeof electricalcomponentsthatcanbeproducedanddirectlyintegratedinlowcostreelto-reelprocesses.
Intelligentpackaging,lowcostRFID(radio-frequencyidentification)transponders,rollabledisplays,flexiblesolarcells,disposablediagnosticdevicesor games,andprintedbatteriesarejustafewexamplesofpromisingfieldsof applicationfororganicelectronicsbasedonnew,largescaleprocessable,electricallyconductiveandsemi-conductingmaterials.
Thefollowingpagespresentashortoverviewoforganicelectronicsapplications,technologiesanddevices,aswellasadiscussionofthedifferenttechnology levelsthatcanbeusedinmanufacturingorganicelectronicproducts,basedonthe thirdeditionoftheroadmapdevelopedbytheOE-A.Sincethesecondeditionwe haveaddedfurtherapplicationsthatweexpecttoplayakeyroleinthecommercializationofthisemergingtechnologyandtakenaccountoftheexciting technicalprogressmaderecently.
Intheapplicationssectionwhichfollows,themarketentryonlargerscalesfor thevariousapplicationsisforecasted.Thekeyapplicationandtechnology parametersrelatingtotheseapplicationsandtheprinciplechallenges(so-called redbrickwalls)toachievingthesehavebeenidentified.Inthesubsequenttechnologysectionwesummarisetheprojecteddevelopmentofrelevanttechnologies andtakeaccountofrecentprogressinnewmaterialsandimprovedprocesses.
AWhitePaperexplainingthecurrenteditionoftheroadmapinmoredetailcan bedownloaded[1].
Organicelectronics Organicelectronicsisbasedonthecombinationofanewclassofmaterials andlargearea,highvolumedepositionandpatterningtechniques.Often termslikeprinted,plastic,polymer,flexible,printableinorganic,largearea orthinfilmelectronicsorabbreviationslikeOLAEorFOLAE(Flexibleand/ orOrganicLargeAreaElectronics)areused,whichessentiallyallmeanthe samething:electronicsbeyondtheclassicalintegratedcircuitapproach.For simplicitywehaveusedthetermorganicelectronicsinthisroadmap,but keepinmindthatweareusingtheterminthisbroadersense.
1.2Applications Organicandprintedelectronicsisaplatformtechnologythatisbasedonorganic conductingandsemi-conductingaswellasprintableinorganicmaterials.Itopens upnewpossibilitiesforapplicationsandproducts.Anumberofkeyapplicationsof organicandprintedelectronicshavebeenchosentodemonstratetheneedsfrom theapplicationside,identifymajorchallenges,crosscheckwiththepossibilitiesof thetechnologyandtoforecastatimeframeforthemarketentryinlargevolumes.
Below,wecontinuetolookatapplicationsdiscussedinthesecondeditionofthe roadmap.i.e.organic photovoltaiccells(OPV),printed RFIDs,organic memories, organic sensors,flexible batteries and smartobjects.Wealsoexpandonthepreviousapplicationareaoforganicthinfilmtransistor(OTFT)displaybackplanesto lookat flexibledisplays,andlookattwonewapplicationareas,electroluminescence (EL) andorganicLED (OLED)basedlighting and smarttextiles.
Thegrowinglistofapplicationsreflectsthecomplexityofthetopicandthewide possibleusesfororganicelectronics,anditislikelythatthelistwillevengrowin thefuture.Theapplicationfieldsandspecificationscoverawiderange,and althoughseveralparameterslikeaccuracyofthepatterningprocessorelectrical conductivityofthematerialsareofcentralimportance,thetopiccannotbereduced toonesingleparameteratthetimebeing,asisknownfromthefamousSilicon Roadmap(Moore’slaw).Regardless,wewillwatchthetrendsandfindoutwhether itwillbepossibletofindananaloguetoMoore’slawfororganicelectronics.
Thequestionwhetherthereisone‘‘killerapplication’’fororganicelectronics cannotbeansweredatthismoment.Therearemanydifferentfieldsinwhichthe advantagesoforganicelectronicsmightresultintherightproducttobecomethe killerapplication,butatthispoint,itistooearlytodefinewhichoneitis.Past experiencewithnewtechnologieshasshownthatthepredicted‘‘killerapplications’’arefrequentlynottheonesthatreallyopenupthelargestmarkets. Therefore,onehastocontinuetheworkontheroadmap,asisplanned,followthe actualtrendsandtakeaccountofnewdevelopmentsastheyoccur.
Firstorganicelectronicproductsreachedthemarketin2005/2006.OLED displaysarenotspecificallycoveredassuchinthisversionoftheroadmapbutare alsobasedonorganicsemiconductors,andarestartingtoseesubstantialmarket penetrationinrecentyears.PassiveIDcardsthataremassprintedonpaperandare usedforticketingortoyswerepresentedin2006[2].FlexibleLithiumbatteries— producedinareel-to-reelprocess—havebeenavailableforseveralyearsandcan beusedforsmartcardsandothermobileconsumerproducts[3].Printedantennae arecommonlyusedin(stillSi-based)RFIDtags.Large-areaorganicpressure sensorsforapplicationssuchasretaillogisticshavealsobeenintroduced,ashave printedelectrodesforglucoseteststrips.Recently,firstOPV[4, 5]andOLED lightingbasedproducts[6, 7]havebecomeavailableandfirstusertestsofsmart cardswithbuilt-indisplaysforone-timepasswordapplicationshavebeenstarted.
Additionalproducts,likeglass-freehighresolutione-readersorrollabledisplayswithorganicTFTbackplanes,printedradiofrequencytagsandorganic
Fig.1.1 Bagwithintegrated OPVbatterycharger. Source Neubers
memories,havealreadybeendemonstratedtechnicallyandhaverecently approachedthemarket.Within2–4years,itisexpectedthatmassmarketswillbe reachedandthatalltheabovementionedapplications,andseveralmore,willbe availableinlargevolumes.
1.2.1ApplicationsRoadmap Dyesensitisedsolarcell(DSSC)based organicphotovoltaic productshavebeen producedcommerciallysince2007[8].FirstpolymerOPVproductshavebeen shipped,withincreasingcommercialavailability,e.g.asflexiblesolarcells(see Fig. 1.1)forabatterychargerformobilephones.ForthenextfewyearsOPVwill primarilyaddressconsumer,outdoorrecreationalandinitialoff-gridmarkets,but asefficiencyandlifetimeimprovethetargetistomoveintobuildingintegratedPV (BIPV)andoff-gridpowergenerationmid-termand,inthelongterm,entertheongridpowergenerationmarket.Thiswillrequiresignificanttechnicalprogressin materialsandprocessestodeliverhighefficiency,highlystableproducts.Inthis bookorganicphotovoltaicsarefurtherdiscussedin Chap2.
Flexibledisplays arestartingtoenterthemarket,withrolltorollproduced segmentedelectrophoreticpricelabelsalreadybeingusedinstoresandrollable e-readerdeviceswithOTFTbackplanes(Fig. 1.2)andlargeareaunbreakable OTFTbasede-readerproductstestmarketed2011.Displaysbasedon electrophoretic or electrochromic mediaoron OLEDs arecurrentlygettinga particularlylargeamountofattention,butdisplaysbasedon liquidcrystals, electrowetting etc.arealsopossible.Furtherinthefuture,bothreflectiveand emissivecolourdisplaysandlargeareaproductslikerollableOLEDTVsor electronicwallpaperareanticipated.However,themovetocolour,highresolution andOLEDswillrequiresignificantimprovementsinbackplanepatterningtechnology,displaymediaandOTFTtechnology.
Fig.1.2 Rollable electrophoreticdisplayfor e-readersandmobilephones. Source Polymervision
Electroluminescent(EL)andOLEDLighting isanapplicationthatisnewto thethirdeditionoftheroadmap.WhileOLEDshavebeenpenetratingthedisplay marketforsometimenow,onlyrecentlyhavesignificantimprovementsinefficiency,lifetimeandlargeareadevicesmadeOLEDanimportantpotentialsourceof novellarge-area,energyefficientsolid-statelighting.ELsignageandbacklighting isalreadycommercial,firstOLEDdesignerlamps(Fig. 1.3)arealreadyavailable, andinthefutureOLEDlightingwillmovefrombeingatechnologyfordesignand decorativeapplicationstotechnicallightingandgeneralillumination;thiswill however,requirebothveryhighefficiency,colourpurityandlifetimeaswellas developmentofprocesses,materialsandarchitecturestocutproductioncosts.
Chap.4 ofthisbookfurtheraddressesOLEDlightinganditsapplications.
PrintedRFID (radiofrequencyidentification)basedonorganicelectronics showedsignificanttechnicalprogresssincethelasteditionoftheroadmap,with announcementsofadvancessuchasrolltorollprintedhighfrequency(HF)tags with1–4bits,aswellasfirstorganicCMOS-likecircuits[9],128bittransponders [10],andultrahighfrequency(UHF)rectifiers[11],allbasedonorganicsemiconductors.Inaddition,therehasbeenprogresswithalternativeapproachessuch aschiplessRFIDconcepts.Printedantennasarealreadycommoninconventional Si-basedRFIDproducts.Afurtherapproachforprintedtranspondersisbasedon Sinanoparticlesonstainlesssteelsubstrates.Theseapproachesarenotfurther takenintoaccountinthecurrentroadmapdiscussion,asthisroadmapfocuseson organic/printedchipsonplasticsubstrates.TheactivitiesofprintedRFIDare targetingtowardsElectronicProductCode(EPCTM)compatibletagsinthelong term(see Chap.7),eventhoughthegeneralperformanceofprintedRFIDwillbe onalowerlevelcomparedtostandardRFIDtagsforalongtime.Simpleprinted
Fig.1.3 OLEDdesigner lamp. Source OSRAMOpto semiconductors
Fig.1.4 PrintedRFIDtag. Source PolyIC
RFIDtags(Fig. 1.4)werepilotedalreadyin2007andshouldbeingeneral commercialusewithinthenextfewyears.Thefutureisexpectedtobringatrend tolargermemory,andtoUHFaswellasHFtags.Theexpectedapplicationsrange frombrandprotectionintoticketing,identification,automationandlogistics,asthe technologyadvances.DespitesomedelaysinmarketintroductionofsimpleRF circuits,therapidtechnicalprogressintherecentpastmakesusoptimisticthat moreadvancedproductswillactuallybeavailablewithinthenextyears.Keysto thisprogresswillbematurehighvolumeandlowcostproductionprocesses,fast circuits,smallerdimensionsandCMOS-likecircuitdevelopment,aswellas appropriatestandardsfororganicRFIDproducts.RFIDsarethemainsubjectof Chaps.6 and 7 ofthisbook.
Fig.1.5 Gamecardswith organicNV-RAM. Source Thinfilmelectronics
PrintedMemory deviceshavealreadybeenintroducedtothemarketinthe formofRead-onlyMemories(ROM)orWriteOnceReadMany(WORM) memoriesinIDorgamecards.Recentlyreeltoreelfabricationofprinted rewritablenon-volatileRandomAccessMemories(NV-RAM)wastechnically demonstrated[12],andfirstlow-densitypolymerNV-RAMproductsareavailable onthemarket(Fig. 1.5).Futuregenerationsofprintedmemoryproductswillseea trendtohigherbitdensity,fasterreadingandwriting,on-boardreadoutandatrend tomoreNV-RAM,thoughROMandWORMwillremainimportant.Keytechnicalissuestoresolveinthefuturewillincludescalingofon-boardreadout electronicsandmemorycells.
OrganicSensor devices(Fig. 1.6)openupavarietyofapplications.Thefield hasdevelopedmorerapidlythanexpected,withprototypetemperature,chemical andpressuresensorsalreadydemonstrated.Temperature,pressureandphotodiode sensorsandsensorarrayswillreachthemarketinthenextfewyears.Onetrend willbefromyes/nosensorstoanalogsensorsabletogiveaquantitativereadout. Forexample,potentiometricsensorsforchemicalanalysisarealreadystartingto becomeavailableinayes/noconfigurationbutanalogversionswillbeavailable midterm.Inthelongterm,combinationofsensordevicesintoembeddedsystems includingon-board(organic)circuitryandpossiblyon-boarddisplay-basedreadoutisexpectedtoenableintelligentsensorsystems.Thiswillrequiresignificant advancesnotonlyinthesensorsthemselvesbutalsointheassociatedon-board circuitry,whichwillrequirehighreproducibility,reliability,yield,etc.Sensorsare furtherdiscussedin Chap.8 ofthisbook,whileintegrationwithcircuitstoenable intelligentsensorsystemsisaddressedin Chaps6 and 7
Thinand flexiblebatteries (Fig. 1.7)arealreadycommerciallyavailablefor discontinuoususe,butthereisroomforimprovementinprice,capacityandeaseof integrationintosomesystems.Overthenextfewyearsatrendtocommercial availabilityofcost-effectivelowcapacitybatteries,thenhighercapacitybatteries forcontinuoususeandfinallybatteriesthatcanbedirectlyprintedintoelectronic
Fig.1.6 Large-areaorganic basedpressuresensorarray.
Source Plasticelectronic
Fig.1.7 Ultraslimprimary batteriesformobiledevices.
Source VARTAmicrobattery
systemsorpackagesisexpected.Keyareasfordevelopmentwillbeoptimisation ofcost-effectiveproductionandencapsulationofLibasedthinbatteries.
Abigadvantageoforganicelectronicsisthecombinationandsimpleintegrationofmultipleelectronicsdevicestocreate smartobjects.Assimple example,printedkeypads,printedloudspeakersandsmartcardsincorporatingthin filmbatteriesandflexibledisplays(Fig. 1.8)havebeenshown[13].Inthefuture thetrendwillbetowardsinclusionofmoredifferentfunctionalitiesaswellasmore complexfunctionalities,movingfromsimpleinputdevices,animatedlogosor smartcardstoobjectswithfulldisplays,intelligentticketsandsensors,games,and smartpackages.Thevarietyofsmartobjectswillbelimitedonlybythenumberof organicelectronictechnologiesavailableandthecreativityofproductdevelopers. Oneofthekeyissuestolookatwillbetakingcareofmechanicalandelectrical compatibilityandconnectionbetweenthedifferentfunctions.
Anothernewapplicationinthecurrentroadmapis smarttextiles,inwhich functionalitiessuchascommunication,displays,sensors,orthermalmanagement
Fig.1.8 Smartcardwith flexiblebatteryand electrochromicdisplay.
Source OE-A
areintegratedintofabrictoenablewearableelectronics(Fig. 1.9).Firstexamples ofintegrationofLEDs,opticalfibersorelectroluminescentelementsintoapparel arealreadystartingtohitthemarket[14, 15].Applicationareasrangefromsport, fashion,safetyandhealthclothingtoarchitecture,andovertimethetechnology willbecomemorecomplex,movingfromsimplesensors,keypads,lighteffects etc.intheshorttermtomorecomplexsystemsincorporatingfunctionalitieslike OPV,fuelcellandtextilesensorsinthefuture.
Theseapplicationscenariosaresummarizedinthe OE-Aroadmapfororganic electronicsapplications inFig. 1.10.Foreachofthenineselectedapplications weshowproductsthatareexpectedtoreachthemarketintheshort(2009–2012) andmediumterm(2012–2017).Wealsogiveaforecastforthelongterm,from 2018onward.Suchasummaryovermanyapplicationsisbynecessitynotdetailed; foreachapplicationareaindividualroadmapshavebeenprepared(seeforexample roadmapsforRFIDandOPVinFigs. 1.11 and 1.12).Figure 1.10 isahigh-level overviewforthewholefieldoforganicandprintedelectronicsthathasbeen distilledfromtheindividualroadmaps.
Thislistofproductsreflectstheideasfromtoday’spointofview.Pastexperience ofnewtechnologyshowsusthatwearemostlikelytobesurprisedbyunexpected applications,andthiswillalmostcertainlyhappenintheexcitingbutnascentfield oforganicelectronics.Thereforethetechnologyandthemarketinthisfieldwill continuouslybewatchedandtheroadmapwillbeupdatedonaregularbasis.
Significantprogresshasbeenmadeinthelastseveralyearsandfirstgenerations ofproductshavealreadybeenenabled.However,inordertofulfilthemore demandingspecificationsofmorecomplexfuturegenerationsofproducts,further improvementofmaterials,process,designandequipmentisnecessary.Inthenext sectionwelookatsomeofthemainapplicationparameterswhosedevelopment willbekeytoenablingfutureproductgenerations.Afterthatwewilllookatthe maintechnologiesinorganicelectronicsanddiscussthekeytechnologyparametersunderlyingtheapplicationparameters.
Fig.1.9 Sportsjacket includingsmartfunctions.
Source Francital
1.2.2KeyApplicationParameters Theviabilityofeachapplicationorproductwilldependonfulfilmentofanumber ofparametersthatdescribethecomplexityorperformanceoftheproduct(applicationparameters).Fortheapplicationsdescribedabovegroupsofspecialists identifiedthemostimportantapplicationandtechnologyparametersand requirementsfordifferentgenerationsofproducts.Herewelistonlyasmall excerptofthekeyapplicationparametersthathavebeenidentifiedasrelevantto severaloftheapplications.Thefollowinglistisinnoparticularordersincethe relevanceofthedifferentparametersvariesforthediverseapplications.
• Complexityofthedevice
Thecomplexityofthecircuit(e.g.numberoftransistors)aswellasthenumber ofdifferentdevices(e.g.circuit,powersupply,switch,sensor,display)thatare integratedhaveacrucialinfluenceonreliabilityandproductionyield.
• Operatingfrequencyofthecircuit
Withincreasingcomplexityoftheapplication(e.g.increasingmemory capacity)higherswitchingspeedsarenecessary.
Fig.1.10 OE-ARoadmapfororganicelectronicsapplications.Forecastforthemarketentryin largevolumes(generalavailability)forthedifferentapplications.SourceOE-A
• Lifetime/stability/homogeneity
Lifetime(shelfandoperation),theenvironmentalstability,stabilityagainst othermaterialsandsolvents,andhomogeneityofthematerialsareissuesdueto theintrinsicpropertiesofthematerialsusedinorganicandprintedelectronics.
• Operatingvoltage
Formobiledevicespoweredbybatteries,PVorradiofrequency,itisessential tohavelowoperatingvoltages(\10V).
• Efficiency
Theconversionefficiencyoflighttoelectricityorelectricitytolightisakey parameterforphoto-voltaiccellsandphotodiodesorOLEDs,andpowerefficiency
OE-A RoadmapforOrganic/ PrintedRFID
Product Generations
Item leveltagging, EPC, identification
96+bit HF + UHF standardized Generalavailability Labdemos, prototypes
16–64bit HF 1–8 bit HF
©OE-A 2009
logistics, automation
Brand protection, e-ticketing,
Short term (2009-2012)
term (2012-2017)
Maturity
term (2018+)
Fig.1.11 ApplicationsroadmapforprintedRFID. Source OE-Aimageand Source PolyIC
OE-A RoadmapforOrganicPhotovoltaics
η≤ 15 % > 10 years < 3 €/Wp
η≤ 10 % ≤ 10 years < 5 €/ W p
η≤ 3 % ≤ 3 years ~ 10€/Wp η≤ 5 % ≤ 5 years < 10€/Wp
©OE-A 2009
Product Generations
Labdemos,prototypes Generalavailability grid
Short term (2009-2012)
Off-grid buildings Facade & BIPV
Maturity
term (2012-2017)
term (2018+)
Fig.1.12 ApplicationsroadmapforOPV. Source OE-Aimageand Source Konarka
ofcircuitryisalsoimportantformanyapplications,especiallythosewhichare mobileandneedtobelightweight.
• Cost
Althoughmostapplicationstargetnewapplicationsandmarketsratherthan replacements,costshavetobelow.Forsomeapplications,suchasrollable
displays,acostpremiumoverconventionalrigiddisplaysmaybeaccepted, whileforotherapplications,e.g.inpackaging,lowcostwillbeamajordriving factor.
1.3Technology Aswehavementionedbefore,weusethetermorganicelectronicsforbrevityto refertothefieldofelectronicsbeyondclassicalsiliconICapproaches,butinclude conceptssuchaslargeareaorflexiblecircuitsandprintedinorganicmaterials. Althoughsomeclassic device conceptsareused, materials, including substrates, and patterningprocesses areverydifferentfromthoseusedintheconventional electronicindustry.Inthissectionwereviewkeymaterials,processesanddevices fororganicelectronicsanddiscussthekeytechnologyparametersthatarecritical fordevelopmentoffutureproducts.Amoredetaileddescriptionoftheprintingand otherpatterningprocesses,materialsanddevicescanbefoundinanarticleinthe 1steditionoftheOE-Abrochure,publishedin2006[16]andin Chap.2 ofthis book.
1.3.1Materials Organicelectronicsrelyonelectricallyactivematerialssuchasconductors, semiconductors,dielectrics,luminescent,electrochromic,electrophoreticor encapsulationmaterials.Thematerialshavetobecarefullychosensinceprocess conditionsandtheinterplaywithotherlayershavealargeinfluenceontheperformanceofthedevice;forexamplethechoiceofappropriatedielectricsandof encapsulationmaterialscanbecriticalfortheperformanceandthestabilityofan organicelectronicproduct.Inthiseditionoftheroadmapwehavefocusedprimarilyonconductingandsemiconductingmaterials,thoughinfutureeditionswe plantoincludeotherclassesofmaterialsaswell.
Therearemanyapproachesonthematerialsideandtheprosandconsofthe differentapproaches—organicorinorganic,solutionbasedorevaporated—arestill underdiscussion.Itisverylikelythatseveralapproacheswillbeusedinparallel.
Organic conductors suchasPEDOT:PSSarestartingtobewidelyusedfor electrodesinavarietyofapplications.Organicconductorscanbehighlytransparent,andwithrecentprogressinconductivityPEDOT:PSSisstartingtobecome arealisticreplacementforIndiumtinOxide(ITO)insomeapplications (Fig. 1.13).Inorganicmaterialslikesilverandothermetals(e.g.asfilledpastesor ultra-thinfilms)arealsousefulifstillhigherconductivityisneeded.
Organic Semiconductors areusedinnumerousactivedevicesandmanyof themaresolutionprocessableandcanbeprinted.Figure 1.14 showsthestructures oftheorganicconductorPEDOT:PSS,ofthecommonpolymersemiconductor
Fig.1.13 ProgressoftheelectricalconductivityofPEDOT:PSS-dispersionsoverthepast 10years. Source OE-A
poly-3-hexyl-thiophene(P3HT),andofthewidelyusedmolecularsemiconductor pentacene[17–19].Organicsemiconductormaterialsarestartingtobeavailableas pre-formulatedinks(seeFig. 1.15).Thechargetransportpropertiesdependon boththemolecularstructureandthedepositionconditionssuchassolvents, depositiontechnique,concentration,interfacesetc.Mostoftheorganicsemiconductorsusedtodayarep-type(likepentaceneandpolythiophene),butn-type materialsarebecomingmorewidespread;havingbothp-andn-typematerials enablesCMOS-typecircuits,whichhavesignificantadvantages,e.g.lowerpower consumption.Thechargecarriermobilityoforganicsemiconductors,thoughstill muchlowerthancrystallinesilicon,hasimproveddramaticallyinrecentyears, alreadymatchingamorphoussilicon(a-Si),andisexpectedtoapproachormatch polycrystallinesilicon(poly-Si)incomingyears,firstinresearch,wheremobilities ofupto2.5cm2/Vshavealreadybeenreported,andsometimelaterincommercialproducts(Fig. 1.16)[20].Thiswillbepossiblewithoptimizedsmall moleculematerialsandpolymersornewmaterialsase.g.inorganics,nanomaterials,carbonnanotubesorhybridmaterials.
Smallmolecule organicsemiconductorsareofgrowinginterest.Thesematerialshaveusuallybeendepositedbyvacuumevaporationorothervapour-phase processes,butmorerecentlydepositionisnolongerrestrictedtoevaporation processes;severalsemiconductorsofthistypecanbeprocessedinsolutionor dispersionandthereforearecompatiblewithsolutioncoatingormassprinting processes.Inaddition,highthroughputevaporationprocessesmightenablethe large-scaleuseofthisclassofmaterials.
Inorganicmaterialssuchas metaloxides [21]or solutionprocessibleSi [22] havealsogeneratedmuchinterestrecently;thesecanbedepositedbyvapour phaseprocessesorfromsolutionasnanoparticlesorprecursors,withreported mobilitiesintherangeofpoly-Siformetaloxidesandevenhigherforsolution
Conductivityof theTransparent OrganicConductors
Fig.1.14 Structuresofcommonmaterialsfororganicelectronics. a conductorPEDOT:PSS. b semiconductorpolythiopheneP3HT. c semiconductorpentacene. Source OE-A
Fig.1.15 Readytousetransparentconductivepolymersolutions. Source H.CStarckClevios
processibleSi.Anopenissuewiththisclassofmaterialsisstilltherelativelyhigh processingtemperatureneededtoachievehighperformance.
Newmaterialclasseslikecarbon nanotubes or hybrid(organic–inorganic) material combinationscouldenablefurtherimprovementsintheperformanceof thedevices.Nanotubeshavebeenusedbothassemiconductorsandasthebasisfor transparentconductingfilms[23].
Aprincipleadvantageoforganicelectronicsisthatlarge,flexibleandlowcost substrates canbeused.Polymerfilms(likethepolyestersPETandPEN,orother polymerslikepolyimideorpolycarbonate)aremostwidelyusedtoday,butpaper, cardboard,thinglassandstainlesssteelarealsoprominentcandidates.Special surfacetreatmentorbarrierlayerscanbeaddedifnecessary.Formany
Fig.1.16 OE-Aroadmapforthechargecarriermobilityofsemiconductorsfororganic electronicsapplications.Thevaluesrefertomaterialsthatareavailableincommercialquantities; researchsamplesmayshowsignificantlyhighermobilities.Thevaluesforamorphoussilicon (a-Si)andpolycrystallinesilicon(poly-Si)aregivenforcomparison. Source OE-A
applicationscarefulsurfacetreatmentsuchasplanarisation,orcoatingwithbarrier materialsisnecessary.Pre-heattreatmentcanimprovethethermalpropertiesof somesubstrates.However,alladditionaltreatmentshaveofcoursesomeeffecton thecost.Thematerialbestsuitedforaspecificapplicationdependsontheprocess conditions,surfaceroughness,thermalexpansion,barrierpropertiesandcost.
1.3.2PrintingandPatterningTechniques Awiderangeoflargeareadepositionandpatterningtechniquescanbeusedfor organicelectronics.Mostprominentinthiscontextarevariousprintingtechniques thatarewellknownfromthegraphicartsindustryandenablereel-to-reelprocessing.Anin-depthanalysisofthesetechniquesandtheirapplicationtoorganic devicemanufacturingisgivenin Chap.2 ofthisbook(Konarka).
Examplesoftwohighvolumeprintingprocesses, gravure and screen,are showninFigs. 1.17 and 1.18.
Other massprintingprocesses are offsetlithography and flexography. The lateralresolution(smallestfeaturethatcanbeprinted)typicallyrangesfrom20to 100 lmdependingonprocess,throughput,substrateandinkproperties,butthere hasbeenrecentprogressonmovingtofeaturesizesassmallas10 lm.Film thicknessescanrangefromwellunder1to10 lm.Theseprintingprocessescan haveenormousthroughputandlowproductioncost,butplacedemanding requirementsonthefunctionalinksintermsofpropertieslikeviscosity,and
cannotcorrectforissueslikesubstratedistortion.Massprintingwillbean importantproductionprocessespeciallyforapplicationswherelargearea,high volumesandlowcostsareimportant.Relatedtovolumeprintingareunpatterned solutioncoatingtechniques suchas slot-die,wirebar or curtaincoating (Fig. 1.19).
Ink-jetprinting hasreceivedgrowinginterestasawaytodepositfunctional materials(seeFig. 1.20).Beingink-jetadigitalprintingprocess,wherenoprinting plateisneeded,thistechniqueenablesvariableprintingandcancorrectin-linefor distortions.Ink-jetprintingheaddevelopershavecontinuedtomanufacturefiner andfinerprintingheads,whicharestartingtoenablefeaturesontheorderofafew lm,andthroughputisimprovingwiththedevelopmentofmulti-headprinters.
Laserablation,largeareavacuumdeposition,softlithographyandlargearea photolithographyare furtherpatterninganddepositiontechniques. Someof theseprocessesaresubtractive,i.e.involveremovingunwantedmaterialfroma
Fig.1.17 Gravureprinting process. Source OE-A
Fig.1.18 Screenprinting process. Source OE-A
Fig.1.19 Curtaincoating process. Source Coatema coatingmachinery
Fig.1.20 Ink-jetdeposition mechanism(piezo). Source OE-A
largeareaunpatternedfilm,whileothersareadditive,i.e.onlydepositmaterial whereitiswanted.Sub-lmpatterningtechniquessuchasnanoimprintlithography andmicrocontactprintinghavegainedagooddealofattentionrecentlybutare stillprimarilyusedinresearch.Eachmethodhasitsindividualstrengths,andin general,processeswithahigherresolutionhaveasmallerthroughput(Fig. 1.21). Therearenosinglestandardprocessesinexistencetoday.Decidingwhich printingorotherpatterningprocessisuseddependsonthespecificrequirementsofa particulardevice.Ingeneral,differentprocesseshavetobeusedforsubsequentsteps ofamultilayerdeviceinordertooptimizeeachprocessstep.Theabovementioned processesdifferstronglywithregardtoe.g.resolutionandthroughput,andone systemmayrequiresomehighthroughputstepsfollowedbyhighresolutionprocesses,e.g.depositionoflargeamountsofmaterialusingcoatingormassprinting followedbyfinepatterningofasmallportionofthesurfaceusinglaserablation.
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