Ab‐Initio Investigation of the Band Alignment Between Cu 2 ZnSnS 4 and Different Buffer Materials (Al 2 ZnO 4 , CeO 2 , ZnSnO 3 )

Limited efficiency of Cu 2 ZnSnS 4 (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 Al 2 ZnO 4 , CeO 2 , or ZnSnO 3 to evaluate the band alignment. Strong hole confinement is predicted for the CZTS/Al 2 ZnO 4 and CZTS/ZnSnO 3 interfaces. A small conduction band offset of 0.31 eV is obtained for the CZTS/ZnSnO 3 interface, indicating that ZnSnO 3 should be considered for improving the efficiency of CZTS solar cells.