衬底对开路电压的影响.doc

Substrateeffectsontheelectronicpropertiesofanorganic/organicheterojunction
有机/有机异质结中衬底对电子性质的影响
Theelectronicstructuresofcopper-phthalocyanine/tris
8-hydroxyquinolinealuminumCuPc/Alq3heterojunctionsonMgandindiumtinoxide
ITOsubstrateshavebeenstudiedbyphotoemissionspectroscopy.WhilethetypicalvacuumenergylevellineupoccurredattheCuPc/Alq3junctiononITO,thesamejunctionformedonMgdisplayedvastlydifferentelectronicstructures,showinga0.5eVbandbendingassociatedwiththeformationofaspacechargelayer.ThesubstrateeffectswereexplainedbytheproximityoftheMg’sFermileveltothelowestunoccupiedmolecularorbitalofCuPc,resultinginspontaneouschargetransfer.TheresultsshowthefeasibilityoftuningtheelectronicpropertiesofanorganicheterojunctionviatheFermilevelofthesubstrate.
人们已经通过光激发光谱研究了Cu/Alq3异质结在Mg和ITO衬底上的电子结构。然而典型的能级lineup只发生在ITO衬底上的Cu/Alq3异质结，同样的异质结在Mg衬底上会有完全不同的电子结构，表现出0.5V能带弯曲，形成一个空间电荷层。这个衬底作用是因为Mg的费米能级接近CuPc的LUMO能级，使电荷自发转移。结果表明可以通过调整衬底的费米能级来改变有机异质结的电子性质具有可行性。
Inrecentyears,considerableeffortshavebeendirectedatdevelopinghigh-efficiencyorganicelectronicandoptoelectronicdevices.1–3Inamultilayerdevicestructure,junctionsformedbetweendifferentorganicsemiconductorsplayacrucialroleinvariouselectronicprocessesincludingchargeinjection,electron-holerecombination,anddissociation.3–5Theseprocessesareinfluencedbythediscontinuityinthelocalenergylevelsattheinterface.Thus,anaccuratepictureoftherelativepositionsofmolecularenergylevelsatorganic/organicinterfacesisessentialfortheoptimizationofdeviceperformance.
最近几年，研发高效率的有机电子和光电子器件方面取得了很大的进步。在多层器件结构中，有机半导体之间的结起到关键作用，不同有机半导体之间的结具有不同的电子活动如电荷注入、电子-空穴复合和激子解离。这些电子活动受到界面处能级不连续性的影响。因此，为了优化器件性能，有必要画出有机/有机界面处分子能级的相对位置。
StudiesinthepastshowthattheassumptionofvacuumlevelalignmentintheSchottky-Mottmodeldoesnotgiveanaccurateaccountoftheelectronicstructuresofmetal/organicinterfaces.6–9Infact,aninterfacialdipole

ofabout0.5–1eVexistsatmostmetal/organicjunctions.6–9However,exceptforsomespecificinterfaces,energeticsforthemajorityofundopedorganic/organicheterojunctionsaresee