Evaluation of different buffer materials for solar cells with wide-gap Cu2ZnGeS: XSe4- x absorbers

Abstract

In this work kesterite-type Cu2ZnGeSxSe4-x (CZGSSe) absorbers were coated with four different buffer layer materials: CdS, In2S3, Zn(O,S) and CdIn2S4. A detailed electrical characterization of the resulting solar cells was performed. The highest open-circuit voltage and the best band alignment could be reached with Zn(O,S), whereas the CdS buffer gave the best efficiencies of up to 6%, which is the highest reported efficiency for a CZGSSe absorber.