Properties of sputter-grown CuGaS2 absorber and CuGaS2/Cd1-xZnxS buffer heterointerface for solar cell application

Abstract

In realizing wide-bandgap CuGaS2 (CGS) based solar cells, CGS thin film deposition methods and suitable n-type buffer layers need to be studied. Even though CGS belongs to the same chalcopyrite family as the more extensively-studied Cu(In,Ga)Se2, their different nature of defects and band profile require a different thin-film deposition approach as well as a careful tuning of the band alignment at the p-n heterojunction. This study focuses on the material properties of sputter-grown CGS films as absorber layer and the heterointerface between CGS absorber and Cd1-xZnxS buffer layer. A moderate amount of Zn is found to be effective in widening the bandgap of the buffer layer while suppressing undesirable absorption loss of high energy photons. Improved optical and structural properties and photocurrent generation are observed from solar cell structure with a sputter-grown CGS absorber with Cd1-xZnxS buffer layer.