Cliff-like conduction band offset and KCN-induced recombination barrier enhancement at the CdS/Cu2ZnSnS4 thin-film solar cell heterojunction

The electronic structure of the CdS/Cu2ZnSnS4 (CZTS) heterojunction was investigated by direct and inverse photoemission. The effects of a KCN etch of the CZTS absorber prior to CdS deposition on the band alignment at the respective interface were studied. We find a cliff-like conduction band offset at the CdS/CZTS interface independent of absorber pretreatment and a significant etch-induced enhancement of the energetic barrier for charge carrier recombination across the CdS/CZTS interface. (C) 2011 American Institute of Physics. [doi:10.1063/1.3663327]