Fabrication of graded band-gap Cu(InCa)Se2 thin-film mini-modules with a Zn(O,S,OH)(x) buffer layer

High-performance Cu(InGa)Se-2 (CIGS) thin-film absorbers with an intentionally graded band-gap structure have been fabricated by a simple two-stage method using In/Cu-Ga/Mo stacked precursors and H2Se gas. Additional sulfurization step to form a thin Cu(InGa)(SeS)(2) surface layer on the absorber is necessary to enhance the grain growth and improve the device performance. Improvement of the interface quality between the absorber and the Zn(O,S,OH)(x) buffer layer by applying a post-deposition light soaking has, for the first time, resulted in the efficiency of over 14% measured by JQA with a 50 cm(2) aperture-area monolithic mini-module. The post-deposition light-soaking treatments would be utilized as an effective tool leading to the accelerated process development with high yield for the future commercial production.