电化学阻抗谱简介 (EIS)课件

电化学阻抗谱简介(EIS)

－TypicalapplicationexamplesinDSCandCIS

solarcells503，StateKeyLaboratoryofCatalysis2007年11月20日Seminar2内容概要关于EIS方法什么是EIS方法?EIS测量有哪些特点?哪些体系适合进行EIS测定?如何测量得到EIS?EIS测量结果的有哪些表达形式?IS在DSC和CIS电池中的应用举例什么是EIS?EIS：ElectrochemicalImpedanceSpectroscopy别名：交流阻抗(ACimpedance)定义：是一种以小振幅的正弦波电位(或电流)为扰动信号的电化学测量方法。电极系统角频率为正弦波信号X电流或者电位电位或者电流角频率为正弦波信号Y在一系列下测得的一组这种频响函数值就是电极系统的EIS，即G()～曹楚南、张鉴清著，《电化学阻抗谱导论》，2002年Y=G()XG()为阻抗或者导纳哪些体系适合进行EIS测定?因果性条件当用一个正弦波的电位信号对电极系统进行扰动，要求电极系统只对该电位信号进行响应。线性条件只有当一个状态变量的变化足够小，才能将电极过程速度的变化与该状态变量的关系近似作线性处理。稳定性条件电极系统在受到扰动后时，其内部结构所发生的变化不大，可以在受到小幅度扰动之后又回到原先的状态。曹楚南、张鉴清著，《电化学阻抗谱导论》，2002年如何测量得到EIS?装置简图相应的操作软件Potentiostat(EG&G,M273)Lock-inamplifier(EG&G,M5210).EIS测量结果的表达形式Y=G()XG()为阻抗或者导纳，总称阻纳。它是一个随频率变化的矢量，用变量为f或其角频率为的复变函数表示，可记为：

G()＝G’()＋jG’’()若G为阻抗，则有Z()＝Z’()＋jZ’’()相位角＝arctg(-Z’’/Z’)-Z’’~Z’为阻抗复平面图，也称为Nyquist图；~logf(或log)log|Z|~logf(或log)Bode图EIS测量结果典型示例NyquistRS**Bode特征频率*=1/RC时间常数＝1/*=RC表征界面电荷转移速度快慢semicirclepeak常相位角元件

Constant-PhaseElement(CPE)Q弥散效应：固体电极的电双层电容的频响特性与“纯电容”并不一致，而有或大或小的偏离的现象。0<n<1曹楚南、张鉴清著，《电化学阻抗谱导论》，2002年串联阻抗(RS)ElectrolyteresistanceElectroderesistanceInterfacialresistancebetweenelectrodeandTCOSchematicdiagramofDSCB.-K.Koo,etal,JElectroceram.2006,17,79-82EquivalentcircuitApplicationinthemeasurementofconductivityInitial:17ohmAfter5days:62.5ohmB.-K.Koo,etal,JElectroceram.2006,17,79-82CNTPtNosignificantchange电极过程研究FrequencyHigh(kHz)Low(mHz)Middle(10~100Hz)Charge-transferattheplatinumcounterelectrodePhotoinjectedelectronswithintheTiO2NernstiandiffusionwithintheelectrolyteAtypicalEISforDSCThreesemicirclesintheNyquistplotThreecharacteristicfrequencypeaksinaBodephaseanglepresentationR.Kern,etal,Electrochimica

Acta.2002,47,4213-4225过程研究示例1：Nyquist图Kuo-ChuanHoGroup,SolarEnergyMater.&SolarCells,2006,90,2398-2404Kuo-ChuanHoGroup,SolarEnergyMater.&SolarCells,2006,90,2391-2397MichaelGrätzelGroup,JACS,2006,128,4146-4154R.Kern,etal,ElectrochimicaActa.2002,47,4213-4225过程研究示例2：Bode图JianbaoLiGroup,Electrochem.Commun.2006,8,946-950WarburgimpedanceFinitediffusionimpedance过程研究示例3：Nyquist图BackgroundandexperimentalTypetransformationinCuInSe2andCuInS2solarcellsisanimportantissuewithfarreachingconsequences.p-type(Cu-rich)n-type(Cu-poor)Inthepresentstudy,thepresenceofap-nhomojunctioninsideCuInS2inaTiO2/CuInS2deviceisrevealedwithadetailedimpedancespectroscopyandcapacitancestudy.n-TiO2140nmp-CuInS2130nmTCO40nmn-CuInS2Carbonspot(graphiteconductiveadhesive,2.3mm)Spraypyrolysisn-n-psystemTechniquesforthemeasurementofhomojunctioninCISElectron-beam-inducedcurrent(EBIC)onlythicktype-convertedCuInSe2layersseveralmicrometersSecondaryionmassspectroscopy(SIMS).onlythicktype-convertedCuInSe2layersseveralmicrometersImpedancespectroscopy(IS)Monitorthepresenceofan-typeregioninCuInS2withunprecedentedaccuracy.Determinethethickness,aswellastheeffectivedonorandacceptordensities.Findouttheenergypositionsoftheinvolveddeepacceptorstateanddeepholetrapbymeasuringthetemperaturedependenceoftheinterfacecapacitance.ISofTiO2/CuInS2devicesatdifferentpotentialsandtemperaturesForfrequenciesabove100kHz,theR1C1branchdominatesovertheothers.

Accordingly,at1MHzC1,beingthespace-chargecapacitance,canbecalculateddirectlyfromtheimaginarypartoftheimpedanceZ”.f=100Hz~1MHzC−2-VplotsofaTCO/TiO2/CuInS2/carbon

deviceatdifferenttemperatures.C−2-VequationsdeducedbythesupposedmodelsModelIModelII-AModelII-BModelIIIT<340K340K<T<400KT>400KUponfittingtheaboveexpressionstotheexperimentaldata,usingrelativedielectricconstantsof55foranataseTiO2and10forbothp-andn-CuInS2.ParametersobtainedfromtheC−2-VequationsModelParametersn-CuInS2p-CuInS2II-AThickness(nm)10030ND&NA(cm-3)4×10162×1017II-BThickness(nm)4090ND&NA(cm-3)2×10174×1016Note:T=400KBecausep-CuInS2isfirstlydeposited,modelII-Bismorereasonable.SummaryEISisapowerfultoolforidentifyingelectronicandionictransportprocessesinDSC.ISisatechnologyversatileandsensitivetotheinterfaceandstructureofjunctions.MichaelGrätzelGroup,JACS,2006,128,4146-4154ND&NA~1/Tn-CuInS2p-CuInS2Bothacceptoranddonordensitiesdecreasewithincreasingtemperature,oppositetoourexpectations.T