Evaluation of different buffer materials for solar cells with wide-gap Cu2ZnGeSxSe4−x absorbers

Abstract

In this work kesterite-type Cu₂ZnGeS_xSe_4−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.