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开路电压起源.docx

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Theoriginoftheopen-circuitvoltageinpolyfluorene-based photovoltaicdevices 聚芴材料光伏器件的开路电压的起源 Theinfluenceofdevicestructureontheopen-circuitvoltageofpolyfluorene-basedphotovoltaicdeviceshasbeeninvestigated.Bilayersofhole-andelectron-acceptingpolyfluoreneshavebeenfabricatedusinganaqueous‘‘float-off’’laminationtechniqueandsubsequentlyincorporatedintoorganicphotovoltaicdeviceswitharangeofcathodesandanodes.Ascalingoftheopen-circuitvoltagewithelectrodeworkfunctiondifferencehasbeenobservedwithanadditionalintensitydependentcontributionfromtheactivelayerwithinthedevice.Thisadditionalcontributionisattributedtophotoinducedgenerationofcarriers,wherebyaccumulationofchargeatthepolymer–polymerheterojunctionresultsinadipoleacrosstheinterfaceandgivesrisetoadiffusioncurrentthatmustbecounterbalancedbyadriftcurrentatopencircuit. 本文研究了器件结构对聚芴光伏器件开路电压的影响。我们利用含水剥离贴合技术制备了具有正负电极的有机光伏器件。同时还发现了开路电压与电极功函数差和器件内活性层有一定关系。活性层对开路电压有影响是因为活性层收到光照后产生光生载流子，光生载流子在聚合物异质结处积累产生偶极子，在开路状态下，产生的扩散电流被漂移电流抵消。 I.INTRODUCTION 引言 Thereisincreasinginterestintheuseoforganicphotovoltaicdevicesastheyofferapotentiallycheapalternativetomoretraditionalphotovoltaicmaterialssuchassilicon.However,powerconversionefficienciesarenotyethighenoughfororganicdevicestobecommerciallyviable.Thepowerconversionefficiencyisdetermined,inpart,bytheshortcircuitcurrentandtheopen-circuitvoltageofthedevice.Overthelastfewyears,blendsandbilayersofelectronandholeacceptorshavebeenusedindevicesinsteadofsinglepolymersinordertoincreasetheshort-circuitcurrentbyimprovingchargeseparation.1–3Ithasbeendemonstratedthattheshort-circuitcurrentissensitivetothefilmmorphology,whichcanbecontrolledbyalteringtheevaporationrate,solventtype,ordepositionmethod.4Recentlyithasbeenshownthattheopen-circuitvoltageinorganicphotovoltaicdevicesisalsoaffectedbythemorphologyoftheactivelayer5andbyvariationsintheelectronacceptorstrength.6Consequently,thetraditionalassumptionthattheopen-circuitvoltageisthedifferencebetweentheworkfunctionsofthetwoelectrodesistoosimplistictodescribe