Simulation of CZTSSe Solar Cells with a Hole Transport Layer of Sb₂(S1‐x,Sex)₃

In this study, Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cell with a hole transport layer (HTL) of Sb 2 (S 1‐x ,Se x ) 3 is simulated by Solar Cell Capacitance Simulator (SCAPS). First, the effect of the Sb 2 (S 1‐x ,Se x ) 3 bandgap (E g ) on device performance is analyzed. When E g is 1.5 eV, the valence band offset (VBO) between CZTSSe and Sb 2 (S 1‐x ,Se x ) 3 is −0.003 eV, forming a nearly flat‐band structure that is favorable for hole transport. Subsequently, several key parameters of the device are optimized. The optimal thickness of the absorber layer is 3.5 µm, and the defect density needs to be controlled below 10 13 cm −3 . The optimum thickness of the Sb 2 (S 1‐x ,Se x ) 3 layer is 20 nm, and the ideal doping density is 10 17 cm −3 . The defect densities at the CZTSSe/Sb 2 (S 1‐x ,Se x ) 3 and CZTSSe/CdS interfaces should be controlled at 10 14 and 10 13 cm −2 or less, respectively. The work function of the back‐electrode should be no less than 5.1 eV. Finally, CZTSSe solar cell can achieve the best efficiency of 22.07%. The simulation results demonstrate the potential to provide a new device structure for fabricating high performance CZTSSe devices.