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1、ARTICLEpubs.acs.org/JACSPotential-DependentRecombinationKineticsofPhotogeneratedElectronsinn-andp-TypeGaNPhotoelectrodesStudiedbyTime-ResolvedIRAbsorptionSpectroscopy,†‡,#‡§‡AkiraYamakata,*MasaakiYoshida,JunKubota,MasatoshiOsawa,andKazunariDomen†GraduateSchoolofEngineering,ToyotaTe
2、chnologicalInstitute,2-12-1Hisakata,Tempaku,Nagoya,468-8511,Japan‡DepartmentofChemicalSystemEngineering,TheUniversityofTokyo,7-3-1Hongo,Bunkyo-ku,Tokyo113-8656,Japan§CatalysisResearchCenter,HokkaidoUniversity,N-21W-10,Kita-ku,Sapporo001-0021,JapanABSTRACT:Recombinationkineticsofpho
3、togeneratedelec-tronsinn-typeandp-typeGaNphotoelectrodesactiveforH2andO2evolution,respectively,fromwaterwasexaminedbytime-resolvedIRabsorption(TR-IR)spectroscopy.Illumina-tionofaGaNfilmwithUVpulse(355nmand6nsinduration)givestransientinterferencespectrainbothtransmittanceandreflection
4、modes.Simulationshowsthattheinterferencespec-traarecausedbyphotogeneratedelectrons.Weobservedthatrecombinationinthemicrosecondregionisgreatlyaffectedbytheappliedpotentials,thelifetimebecominglongeratnegativeandpositivepotentialsforn-andp-typeGaNelectrodes,respectively.Thereisagoodco
5、rrelationbetweenpotentialdependenceofthesteady-statereactionefficiencyandthatofthenumberofsurvivingelectronsinthemillisecondregion.WealsoperformedpotentialjumpmeasurementtoexaminetheshiftinFermilevelbyphotogeneratedchargecarriers.Inthecaseofn-typeGaN,theelectrodepotentialjumpstothene
6、gativesidebyaccumulationofelectronsinthebulk.However,inthecaseofp-typeGaN,theelectrodepotentialfirstjumpstothenegativesidewithin20μsandgraduallyshiftstothepositivesideinafewmilliseconds,whilethenumberofchargecarriersisconstantat>0.2ms.Thistwo-stepprocessisascribedtoelectrontransport
7、fromthebulktothesurfaceofGaN,becausetheelectrodepotentialissensitivetothenumberofelectronsinthebulk.TheresultsconfirmthatTR-IRcombinedwithpotentialjumpmeasurementprovidesusefulinformationforunderstandingthebehaviorofchargecarriersinphotoelectrochemicalsystems.1.INTRODUCTIONspectrosc
8、opy(TR-PL)hasbeenwidelyuse
