Modifying the Hetero-junction Interface of Cu2ZnSnSe4 Solar Cells

CZTSe solar cells are prepared with CBD-Zn(O,S) layer as a buffer layer. By a concentrated ammonium etching and subsequent soft annealing treatment, the detrimental ZnO and Zn(OH)2 secondary phases are eliminated from Zn(O,S) layer, thus restraining the band fluctuation caused by secondary phases and improving the hetero-junction quality significantly. Consequently, the conversion efficiency of the Zn(O,S)/CZTSe solar cells was improved from 1.17% to a favorable value of 7.2%. The results of device analysis indicates a defects level may exists in the Zn(O,S) layer and acts as a shortcut for the transport of negative charge carrier across the Zn(O,S) layer.