Refined optoelectronic properties of silicon nanowires for improving photovoltaic properties of crystalline solar cells a simulation study

TOPICAL REVIEW • OPEN ACCESS Emerging inorganic solar cell efficiency tables (version 2) To cite this article: Andriy Zakutayev et al 2021 J. Phys. Energy 3 032003 View the article online for updates and enhancements. This content was downloaded from IP address 123.139.57.166 on 28/06/2021 at 12:04 J. Phys. Energy 3 (2021)032003 https://doi.org/10.1088/2515-7655/abebca Journal of Physics: Energy OPEN ACCESS RECEIVED 22October2020 REVISED 27January2021 ACCEPTED FOR PUBLICATION 3March2021 PUBLISHED 16April2021 Originalcontentfrom thisworkmaybeused underthetermsofthe CreativeCommons Attribution4.0licence . Anyfurtherdistribution ofthisworkmust maintainattributionto theauthor(s)andthetitle ofthework,journal citationandDOI. TOPICAL REVIEW Emerging inorganic solar cell efficiency tables (version 2) Andriy Zakutayev 1, Jonathan D Major2 , Xiaojing Hao3 , Aron Walsh4 ,5, Jiang Tang6 , Teodor K Todorov 7 , Lydia H Wong 8and Edgardo Saucedo9 ,∗ 1 NationalRenewableEnergyLaboratory(NREL),Golden,CO80401,UnitedStatesofAmerica 2 StephensonInstituteforRenewableEnergy,DepartmentofPhysics,UniversityofLiverpool(UL),LiverpoolL697ZF,UnitedKingdom 3 AustralianCentreforAdvancedPhotovoltaics,SchoolofPhotovoltaicandRenewableEnergyEngineering,UniversityofNewSouth Wales(UNSW),Sydney,NSW2052,Australia 4 DepartmentofMaterials,ImperialCollegeLondon(ICL),ExhibitionRoad,LondonSW72AZ,UnitedKingdom 5 YonseiUniversity(YU),Seoul03722,RepublicofKorea 6 WuhanNationalLaboratoryforOptoelectronics,HuazhongUniversityofScienceandTechnology(HUST),430074Wuhan,People’s RepublicofChina 7 IBMThomasJ.WatsonResearchCenter,YorktownHeights,NewYork10598,UnitedStatesofAmerica 8 SchoolofMaterialsScience HZB, Ge rman y [32 ]. Spin co ating of 2-me tho xy ethanol base d sol utio n. Cu 2Zn(S n0.78 Ge 0.22 )Se 4 12.3 0.527 32.2 72.7 0.519 1.11 Glass/M o/CZT GT Se/CdS/ ZnO/AZ O/A g/AR C EQE, in-house AIST ,Jap an [33 ].C o-e vap orat ion and rea cti ve annealing . (Li 0.06 Cu 0.94 )2ZnS n(S,S e)4 11.6 0.531 33.7 64.8 0.285 1.13 Glass/S iO x/M o/LiCZT SS e/ CdS/ZnO/AZ O/N i/A l/MgF 2 EQE, in-house EMP A,S witz erland; Uni ver sidad Autónoma de Madr id, Sp ain; HZB, Ge rman y[ 34 ].Spin co ating of DMSO base dsol utio n. Cu 2(Zn 0.95 Mn 0.05 )Sn(S,S e)4 8.9 0.418 33.7 63.3 0.34 1.06 Glass/M o/CMZT SS e/CdS/ ZnO/AZ O/N i/A l EQE Nankai Uni ver sity ,China; Nat ional Inst itut eo fM ate rial Scie nce, Jap an [35 ]. Spin co ating of 2-me tho xy ethanol base d sol utio n. Cu 2Zn 0.96 Mg 0.04 Sn(S,S e)4 7.2 0.419 37.2 46.5 0.3 1.01 Glass/S iO x/M o/CZMT SS e/ CdS/i-ZnO/AZ O/N i/ Al/MgF2 Uni ver sidad Autónoma de Madr id, Sp ain [36 ].P recur sor sol utio np repar ed by dime thy lsulf oxid e(DMSO). (C ont inue d) 7 J. Phys. Energy 3 (2021)032003 AZakutayevet al Tab le 2. (C ont inue d.) Mat erial Eff. (%) VO C (V ) JSC (mA cm − 2 ) FF (%) Ar ea (cm 2 ) Eg (eV ) De vic est ruc tur e Means of ver ificat ion Inst itu tio ns and Co mme nts Cu 2S nS 3 5.1 0.290 34.5 51.3 0.3 0.95 Glass/M o/CT S/CdS/ i-ZnO/AZ O/N i/A l EQE, in-house Rits ume ikan Uni ver sity ,Jap an [37 ]. Abso rbe rp repar ed by Spu tte ring of Cu-S nS2 co mp ound, and e-b eam evap orat ion of NaF . Cu 2ZnS n0.91 I0.09 (S,S e)4 7.19 0.393 32.12 56.96 0.21 1.075 Mo-f oil/CZTISS e/CdS/ i-ZnO/IT O/A g EQE, in house Fujian JIangx ia Uni ver sity ,Fuzho u,China [38 ].A bso rbe ris de posit ed on fle xib le Mo foil by spin co ating of pre cur sor sol utio n base do n1,2-e thane dithiol (edtH2) and 1,2-e thy lene diamine (en) sol utio n. Cu 2ZnS nx Ga 1− x(S,S e)4 10.8 0.455 36.48 65.05 0.21 1.162 Glass/M o/CZT GSS e/CdS/ iZnO/IT O/A g/MgF 2 EQE, in house He nan Uni ver sity [31 ].W ith AR C; thin film isd ep osit ed by spin co ating of pre cur sor sol utio nbase do ne thy lendiamine and 1,2 ethane dithiol. Cu 2S n1− xGe xS 3 6.73 0.442 26.6 57.1 0.17 1.09 Glass/M o/CT GS/CdS/ ZnO:Ga/A l EQE, in-house To yota Ce ntr al Res ear ch PC—p htalo cyanine. 11 J. Phys. Energy 3 (2021)032003 AZakutayevet al well-establishedsolarcelltechnologies.However,fortheemergingsolarcelltechnologiesthataredeveloping veryquickly,suchcertificationisnotalwayspractical,soonlyin-housemeasuredphotovoltaic(PV) efficienciesareoftenreported.Thus,itisimportanttoreviewherecommonbestpracticesforin-housesolar cellefficiencymeasurements.Themostbasicrequirementsforlab-basedsolarcellefficiencymeasurements include: (a) usingtheairmass1.5spectrum(AM1.5)forterrestrialcellsbychoosingthehighest-qualitysolarsimu- latoravailable; (b) applyingone-sunofilluminationwithintensityof1000Wcm −2 byadjustingthecell/simulatordistance tomatchtheexpectedcurrentofthereferencecell; (c) controllingcelltemperatureduringthemeasurementto25 ◦Cusingactivecoolingorheating; (d) usingfour-pointprobegeometrytoremovetheeffectofprobe/cellcontactresistance. Inaddition,thereareseveralotherbestpracticestofollow. (a) Areasofthemeasuredsolarcellshavetobecarefullydefinedusingdeviceisolationand/orlightmasking; thisisparticularlyrelevanttoabsorberswithlargecarrierdiffusionlengths. (b) Currentdensity–voltagemeasurementshavetobeperformedinbothforwardandreversedirections, whichisespeciallyimportantforemergingabsorberswithtendencyforhysteresis. (c) EQEmeasurementhastobereportedtoassistwithspectralcorrection,andintegratedwiththeAM1.5 referencespectrumtoobtainthecurrent,tobecomparedtoreportedJsc. (d) Statisticalanalysisresults,includingthenumberofthesolarcellsmeasured,andthemeanvalueshaveto bementioned. (e) Short-timeevolutionofthereporteddeficiencyhastobeverifiedatthemaximumpowerpointorwith thephotocurrentatmaximumpowerpoint. (f) Long-timestabilityanalysisisencouraged,underlightandelectricalbias,withmeasuredtemperature andhumidity. (g) Formulti-junctionsolarcells,theilluminationbiasandvoltagebiasusedforeachcellhavetobereported. Finally,wereemphasizethatthesearejustguidelinesforin-housesolarcellmeasurements,whenexternal certificationisnotpractical.However,researchersworkingonemergingsolarcelltechnologiesarestrongly encouragedtostrivetowardsperfectionandconsidersubmissionoftheirdevicestooneofthe internationallyrecognizedinstitutions. 2.Efficiencytables Table1 presentsthelistofmaterialsthathavebeenidentifiedfortheauthorsascertifiedsolarcells,andare consideredasthehighestreportedconversionefficiencyintheirclassoftechnology.Thelastpartoftable1 collectsthetechnologiesthatbeingcertified,donotfulfilsomeofthecriteriausedforincludingtheminthe principalsection.Table2 containsthelistofmaterialsanddeviceperformancefornon-certifiedsolarcells. Thecombineddatafrombothtablesisplottedinfigure2 ,whereitisseparatedintothreecategories:metal pnictides(e.g.ZnSnP2 ),chalcogenides(e.g.PbS),andhalides(e.g.BiI3 ). 3.Newentries 3.1.Oxides Therehavebeennonewrecordsreportedforsolarcellswithoxideabsorbers,butseveralimportantadvances havebeenmade.ForCu2 OabsorberswithGa2 O3 bufferlayersgrownbychemicalvapourdeposition,the Vocof1.78Vhasbeenachievedalbeitwithsmallphotocurrentof2mAcm −2 [65 ].Thisdemonstratesthe abilityofCu2 Otoreach80%of VocentitlementbasedonShockley–Queisserlimit(Eg =2.2eV),and achieveinthefuture13%efficiencyforthickerabsorberlayersbasedonnumericalmodels[ 66 ].Alow damagemagnetronsputteringmethodforfabricationofZnOcontactstoCu2 Osolarcellshasbeenalso recentlydemonstrated[67 ].TheprogressinCu2 Oandotheroxidesolarcellshasbeensummarizedina recentroadmaparticle[67 ]andabookchapter[68 ]. Asofthemoreexoticoxideabsorberswithperovskitestructureandferroelectricproperties,upto4.2% efficiencyhasbeenreportedinmixed-phaseBiMnO3 andBiMn2 O5 thinfilmabsorbers[18 ].Thereported Vocof1.5V, Jscof7mAcm −2 andfillfactorof0.58havebeenreported(table 2 ).Thisreportcomesfromthe samegroupthatpublishedon3.3%efficiencyinsinglelayersand8.1%inmultilayersofBi 2 FeCrO6 6years ago[41 ].Neitheroftheseexcitingresultspublishedhighprofilejournalshavebeenreplicatedbyother 12 J. Phys. Energy 3 (2021)032003 AZakutayevet al Figure2. Efficiency(a),Voc(b),Jsc(c)andFF(d)ofthemostrelevantthinfilminorganicPVtechnologies,fromtables1 and2 . TheirperformanceiscomparedtothefullShockley–Queisser(SQ)limitfortheAM1.5spectrum(solidgreyline)and50%ofthe SQlimit(dashedgreyline). groups,whichissomewhatconcerning.TheprogressinBiFeO3 derivatives[69 ]andotherperovskitesas photoferroicmaterialshasbeenrecentlyreviewed[70 ]. 3.2.Chalcogenides Fivenewresultsarereportedinthepresentversionforchalcogenides,withtwonewresultsfromkesterite andantimonychalcogeniderespectively,andthreenewentriesfromkesterite.Thefirstnewresultis12.5% efficiencypureselenidekesterite(Cu2 ZnSnSe4 )solarcellfabricatedonglassshownintable1 .Thishighest efficiencypureselenideCZTSesolarcellalsodemonstratesthesmallestVoc-deficit(givenbyEg/q−Voc)of anyreportedkesteritefamilydevices.Thereportedefficiencyimprovementisrealizedbyengineeringthe localchemicalenvironment(i.e.properchemicalcompositionandcompleteoxidationofSntoSn4 +)during thegrowthofkesteritethin-film,particularlyatthepointintimewhentheformationofkesteriteinitiates. Withthisdefectcontrolmethod,thereportedelectricalproperties(i.e.mobility,carrierconcentration)of kesteriteareimprovedandthedetrimentalintrinsicdefectsaresuppressed.Oneofthreenewentriesfor kesteriteintable2 isthemagnesium-alloyedkesterite.TheintroductionofsmallamountofMgintokesterite resultsinthe7.2%efficiencyCu 2 Zn0.96 Mg0.04 Sn(S,Se)4 solarcells.SuchsmallamountMgcanleadtothe changeinlatticeconstantandcarrierconcentrationofkesterite,whichseemstoplayasimilarroletoalkaline Lithium.NotablesubstitutionofgroupIIIelementsofInandGainCu2 ZnSn(S,Se)4 werealsoreportedto improvetheefficiencyeventhoughthereasonsforimprovementsarenotthoroughlyinvestigated[31 ]. Cd-substitutedCZTSisrecentlyreportedwithanewrecordof12.6%[ 30 ]byengineeringthecharge extractionlayers.Wealsonotethatasignificantnumbersofgroupshavereportedefficienciesexceeding12% [8 ,30 ,71 ]andclosingthegapwithworldrecordefficiencyreportedbyIBMin2013[ 6 ].Mostofthese reports,however,havenotcompletelyeliminatedtheoriginofthedeepdefectswhicharewidelybelievedto causebandtailingandthesignificantVocdeficitinthisclassofmaterials.Recenttheoreticalanalysisand experimentalevidenceseemtoindicatethatamajorcontributiontothebandtailsisfromthedeep 2Cu Zn +SnZndefectclusters[72 ,73 ].ThelatestexperimentalevidenceisdemonstratedintheCu2 CdZnS4 (CCTS)whereCdsubstitutionofZninCu-poorCCTSsuppressthedeleterious2Cu Zn +SnZndefectclusters andsignificantlyreducesbandgapfluctuations[21 ].ThisworksetsanewefficiencyrecordinCu2 CdZnS4 with7.96%,whichisthehighestefficiencyamongthenovelcompoundsderivedfromCu–Zn–S/Se. 13 J. Phys. Energy 3 (2021)032003 AZakutayevet al Anothertwonewentriesintable2 arefromsimplechalcogenides,i.e.5.1%efficiencyCu 2 SnS3 and6.73% efficiencyGe-alloyedCu2 SnS3 .NotablethatSn/GegradientisrealizedinthelatterCu2 Sn1 −xGexS3 (CTGS). 3.3.Pnictides TherehavebeenseveralrecentreportsonZnSnP2 basedsolarcells[74 ].Thehighest3.4%efficiencyreported todateisforZnSnP2 singlecrystalabsorberswith(Cd,Zn)Sbufferlayers[17 ],withJscof12mAcm −2 ,Voc of0.47andafillfactorof0.59(table 2 ).ThinfilmZnSnP2 solarcellwithCdSbufferlayerspreparedby phosphidationofZn/Snstackshadmuchlowerefficiencies(0.02%)[ 75 ]comparedtocrystalbased ZnSnP2/CdSsolarcells(2%)[ 76 ].All-phosphideZnSnP2 singlecrystaldeviceswithCdSnP2 bufferlayers showedclearrectificationbehaviourbutnophotoresponse[77 ]. 3.4.Halides ThenumberofpublishedpapersreportinghalidematerialsforPV(mainlyperovskitehalides),areincreasing quickly,andinconsequenceseveralprogresseshavebeenreported.Mostofthehighefficiencyabsorbers becomesfromtheCs–Pbperovskitehalidefamily,andhaveshown1%–3%recordefficiencyimprovementin thelastyear.Someoftheseprogressesarerelatedtotheuseofadditivesforthebestcontrolofgrowth procedureandcrystallizationprocess. CsPbI3 —therecordefficiencyhasimproveduptoanimpressive19.03%.Wang et al[47 ]demonstrated thattheuseofDMAIisveryeffectivetomanipulatethecrystallizationprocessofCsPbI3 ,confirmingthatthe DMAIadditivewouldnotalloyintothecrystallatticeofCsPbI3 perovskite.Furthermore,theuseof phenyltrimethylammoniumchloridepassivatedCsPbI3 inorganicperovskite,allowingfortheimpressive efficiencyimprovement,althoughthereisadebateifDMAandDMAIcansitattheA-sitesoftheperovskite structureandthesematerialsarenon-fullyinorganic. CsPbBr3 —althoughmoremodest,CsPbBr3 hasachievedanewrecordof10.91%.Todoso,Tong et al [46 ]developedagrowthprocedureinducedbyphasetransitionthatmakesthegrainsizeofperovskitefilms moreuniform,andalsolowersthesurfacepotentialbarrierthatexistsbetweenthecrystalsandgrain boundaries. CsPbBrI2 andCsPbIBr2 —inthefirstcaseonlylimitedefficiencyimprovementhasbeenreportedinthe lastmonths,achieving16.79%efficiencyrecordwithandimpressive Vocof1.32V.Thisimprovementwas againrelatedtopassivationeffectandn-typedopingbyintroducingCaCl2 ,observingalsothatthe crystallinityoftheCsPbI2 Brperovskitefilmwasenhanced,andthetrapdensitywassuppressedthroughthe useofCaCl2 treatment[48 ].Inthesecondcase,arecordefficiencyof11.10%hasbeenreportedwithan improvedVocof1.21V,butwithalargeenhancementoftheFFupto74.82%[ 49 ].Thishasbeenpossible thankstotheintroductionofaLewisbase(PEG)asadditiveobservingsuppressednon-radiative electron–holerecombinationandafavourableenergybandstructure. Otherhalideperovskitesdonotreportimportantprogressesintermsofconversionefficiencyinthelast months. 3.5.Mixed-anion Startingfromthissecondeditionoftheefficiencytables,weareincludinganewclassofPVabsorbersbased onmixedantimonyand/orbismuthchalcogenide-halides.SpecialmentionmeritstheworkofNeoandSeok [55 ],whereusingafastvapourprocesstheydevelopedSbSIandSbSI-interlayeredSb2 S3 solarcells, demonstratingaTiO2 /Sb2 S3 /SbSI/HTMdevicewithaconversionefficiencyof6.08%.Efficienciesbetween 1%and4%havebeenalsoreportedforSbSI,(Sb,Bi)SIandBiSIsystems,demonstratingthelargepotential ofthesemixedchalcogenide-halidecompoundsandtheincreasedinterestthatthescientificcommunityis puttinginsuchmaterialsforsolarcellsapplications. 4.Latestprogressesinselectedtopic:Q-1DabsorbersforPV Traditionally,absorbermaterialsforPVsarelimitedtosemiconductorswiththree-dimensional(3D)crystal structure(i.e.GaAs,CdTeandCu(In,Ga)Se2 )thusenjoyingthenearlyisotropicfilmgrowthandcarrier transport.Recently,thepreviouslyabandonedlow-dimensionalabsorbermaterialshaveattractedwide attentionbecauseoftheirsimpleandEarth-abundantcomposition,andperformanceimprovement [4 ,60 ,78 ].Specifically,theQ-1Dbinaryantimony-basedchalcogenide(Sb 2 S3 ,Sb2 Se3 andSb2 (S,Se)3 alloy) solarcellsarenontoxicandstable,andhaveachievedimpressivepowerconversionefficiencyof7%–10% [4 ,12 ,79 ].Q-1DSb-basedchalcogenidesaremadeupofcovalentlybonded[Sb 4 S(e)6 ]n ribbons,andthese ribbonsarestackedviaweakVanderWaalsforcealonga-andb-axis[80 ].Basedondeviceconfiguration, Q-1DSb-basedchalcogenidesolarcellscanbedividedintosensitizedsolarcellsandplanar(superstrateand 14 J. Phys. Energy 3 (2021)032003 AZakutayevet al substrate)devices.Next,wewillbrieflyreviewthemainefficiencyimprovementofQ-1Dsolarcellsineach configuration: Sensitized-typesolarcell.Attheearlyage,Sb-basedchalcogenidesensitized-typesolarcellswasledby SeokgroupfromKoreaResearchInstituteofChemic