Improvement of power conversion efficiency of Cu2ZnSn(S,Se)4 solar cells by Al doped CdS

In this work, we substituted Al doped CdS(CdS:Al) for CdS buffer layer of Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cell to increase built-in field and decrease interface recombination, and studied influence of this substitution on power conversion efficiency (PCE) of CZTSSe solar cell. It is found that the PCE can be increased from 6.57% to 8.99% by substituting CdS:Al with Al doping concentration of 3.3 at% for CdS. The increased PCE is mainly attributed to increase in photogenerated current density ( J L ) and decrease in reverse saturation current density ( J 0 ). Mechanisms of increase in J L and decrease in J 0 are suggested by analysis of influence of change of bandgap, transmission, electron density and lattice constants of CdS induced by Al doping on light intensity passing through CdS, built-in field and lattice mismatch of CZTSSe/CdS heterojunction. This strategy provides a rational design for optimizing the heterojunction of CZTSSe solar cells to achieve high efficiency.