Texturization of silicon wafers with Na2CO3 and Na2CO3/NaHCO3 solutions for heterojunction solar-cell applications
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ISSN: 1369-8001
Publication date
Abstract
Theformationofpyramidalstructuresbyanisotropicetchingof/100S-orientedmono
crystalline siliconwafer surfaces is an effectivemethod to reduce reflection losses
originatingonthefrontsideofconventionalsiliconsolarcellsandsilicon-heterojunction
(SHJ)solarcells.Oneofthemostcommonmethodsoftexturizationusedinthesolar-cell
industry isbasedonaqueous solutionsofNaOHorKOHand isopropyl alcohol (IPA).
However, IPAis toxicandrelativelyexpensive, soeffortsarebeingmadetoreplace it.
Among the potential alternatives, solutions based on Na2CO3 and Na2CO3/NaHCO3
mixtureshavebeenproposed. Inthepresent study, solutionsofNa2CO3 andNa2CO3/
NaHCO3mixtureswerepreparedinordertoformpyramidalstructuresonsiliconwafer
surfaces. Itwasnotpossibletoobtainuniformandcompletelytexturedsurfacesbyusing
aqueoussolutionsconsistingonlyofNa2CO3.NaHCO3mustbeaddedinordertoachieve
uniformtexturedsurfaceswithlowhemispherical reflectancesuitableforSHJ solar-cell
applications. Textured surfaceswithgooduniformity and lowaveragehemispherical
reflectance (15.4%)wereprepared from/100Ssiliconsubstrateswithrelatively low
etchingtimes (25min).Goodsurfacepassivation(lifetime4600msandimplicitopen
circuitvoltageof690710mV)onthesep-typetexturedwaferswereachieved.