Homogeneous Nancorporation for industrial‐scale application of Cu(In,Ga)(Se,S)2 solar cells

摘要

Abstract We achieve large‐area (1602?×?902?mm 2 ) doping uniformity without layer peel‐offs, based on a dual Na source, ie, partial Na out‐diffusion from soda‐lime glass and a homogeneously sputtered CuGa:NaF layer as an auxiliary source. We systematically investigate the optoelectronic, microstructural, and compositional characteristics of Cu(In,Ga)(Se,S) 2 solar cells and analyze the underlying mechanism in detail. Na out‐diffusion from soda‐lime glass initially improves the cell performance according to the defect passivation and Na doping effects; further Na incorporation using the Na‐doped layer enhances J SC , FF, and film conductivity, which is likely due to the enhanced cell homogeneity and the alleviation of carrier transport‐limited characteristics. Excessive Na incorporation triggers the possible generation of layer peel‐offs, which is closely related to the reduced adhesion force, void generation, decrease in S/(S?+?Se) ratio, Ga redistribution, bandgap reduction, and increase in the low‐energy photoluminescence. These results indicate that the voids are created via Kirkendal mechanism based on the variability in atomic diffusion rates following compositional changes, resulting from the insufficiency in Na consumption or sulfurization. It is noted that an in‐line codeposition technique enables realization of high‐level Na doping as well as void‐free interface state by suppressing the defect generation, which yields high‐efficiency commercial‐scale Cu(In,Ga)(Se,S) 2 modules without layer peel‐off problems.