Ab‐Initio Investigation of the Band Alignment Between Cu2ZnSnS4 and Different Buffer Materials (Al2ZnO4, CeO2, ZnSnO3)

Limited efficiency of Cu2ZnSnS4 (CZTS) solar cells due to high recombination rates at the CZTS–buffer interface calls for alternative buffer materials to enhance the open circuit voltage and, therefore, the device performance. By means of ab‐initio hybrid functional calculations, the authors investigate the interfaces between the p‐type absorber CZTS and the n‐type buffer materials Al2ZnO4, CeO2, or ZnSnO3 to evaluate the band alignment. Strong hole confinement is predicted for the CZTS/Al2ZnO4 and CZTS/ZnSnO3 interfaces. A small conduction band offset of 0.31 eV is obtained for the CZTS/ZnSnO3 interface, indicating that ZnSnO3 should be considered for improving the efficiency of CZTS solar cells.