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

Abstract

We achieve large‐area (1602 × 902 mm2) 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 JSC, 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.

Front Transparent Passivation of CIGS-Based Solar Cells via AZO

“…As a matter of fact, we have grown AZO films with similar performances on the large−scale substrate with an area of 100 cm 2 , see the inset of Figure 2 a. Thanks to the high uniformity of AZO, CIGS solar cells are successfully fabricated on a large−scale substrate, displaying high uniformity regarding to V oc , see Figure 1 h. It should be noted that CIGS solar cells are free of Na doping and alkali metal post deposition treatment, which is beneficial to V oc [ 12 , 13 ]. The high uniformity of AZO is helpful to the performance uniformity of CIGS solar cells, as shown in Figure S1, Supporting Information .…”

Toward High-Efficiency Cu(In,Ga)(S,Se)2 Solar Cells by a Simultaneous Selenization and Sulfurization Rapid Thermal Process

“…Typically, there are three methods to provide Se to react for the selenization/sulfurization process to fabricate a CIGS absorber layer. The first method is using hydrogen selenide (H 2 Se) as a selenium source during the high-temperature selenization process to react with the CuGa/In precursor, forming a CIGSe absorber. − H 2 Se is reported to fabricate high-efficiency CIGSe solar cells by improving the crystallinity of the absorber layer and reducing the grain boundary recombination. However, the H 2 Se gas is highly toxic, expensive, and corrosive, thus imposing strict requirements for selenization equipment.…”