Surface Engineering of Submicron Cu(In,Ga)Se2 for High-Efficient Zn(O,S)-Based Solar Cells with Lower Light Soaking Effects

Cu-2(In,Ga)Se-2 thin-film solar cells with Zn(O,S) buffer layers have become the focus of industries due to their favorable features, in particular, their high efficiency. However, the frequently reported light soaking (LS) effect, as a photoinduced metastable phenomenon, was one of the most serious problems suffered by Zn(O,S)/CIGS devices. Unfortunately, the mechanism behind this has not yet been completely revealed. In this paper, the surface components of the submicron CIGS absorption layer (similar to 970 nm) were carefully regulated, thereby effectively suppressing the photoinduced metastable effect on Zn(O,S)/CIGS solar cells. It can be found from the features of the surface and the parameters of corresponding solar devices that an appropriate surface component (GGI similar to 0.348, CGI similar to 0.894) can not only effectively mitigate the LS effect but also increase the conversion efficiency of solar cells, especially the evolution of fill factor, which is impressive. Finally, the combination of appropriate surface regulation and an anti-reflection layer of MgF2 enables us to obtain a 17.6% Cd-free submicron CIGS solar cell with a significantly lower LS effect, representing the highest value in submicron CIGS solar devices. It is hoped that this paper can pave the way for the CIGS absorber layer to suppress the metastable effect.

Automated summary

This study effectively suppressed the light soaking effect in Zn(O,S)/CIGS solar cells by carefully regulating the surface components of the submicron CIGS absorption layer. It increased the conversion efficiency of the solar cells, especially the fill factor. By combining appropriate surface regulation and an anti-reflection layer of MgF2, a 17.6% Cd-free submicron CIGS solar cell with significantly lower light soaking effect was achieved, representing the highest value in submicron CIGS solar devices. This research paves the way for suppressing the metastable effect in CIGS absorber layer.