High-efficiency Cu(In,Ga)Se2 thin-film solar cells with a CBD-ZnS buffer layer

High-efficiency cadmium-free Cu(In,Ga)Se2 (CIGS) thin-film solar cells have been fabricated using a chemical bath deposition (CBD)-ZnS buffer layer, a wider band gap material than of conventional CBD-CdS. Energy dispersive X-ray microanalysis (EDX) revealed Zn interdiffusion in the CIGS thin film at the CBD-ZnS/CIGS solar cell interface, implying formation of a buried np junction at the surface of the CIGS film. The best cell to date yielded an active area efficiency of 17.2% after light soaking. This result suggests that CIGS solar cells with efficiencies as high as those fabricated using CdS buffer can be achieved even if Cd is not utilized.