Numerical modeling of inverted perovskite solar cell based on CZTSSe hole transport layer for efficiency improvement

In this work, device modeling of inverted-structure perovskite solar cells employing Cu2ZnSn(SxSe1−x)4 (CZTSxSe1−x) as hole transport layer (HTL) is performed by SCAPS. The bandgap of CZTSxSe1−x can be tuned in a wide range from 0.95 to 1.5 eV through the variation of S doping content, which allows us to adjust the valence band offset (VBO) of the CH3NH3PbI3/CZTSxSe1−x interface. Simulation results indicate that a suitable VBO of 0.25 eV is obtained when S/(S + Se) ratio of CZTSxSe1−x is 0.6, which yields a cell efficiency of 16.75%. Further optimization of the absorber and HTL thickness and doping density in HTL is conducted. Simulation results indicate that the optimal HTL and absorber thickness of are 30 and 700 nm, respectively. Doping concentration of HTL higher than 1019 cm−3 is essential for good device performance. After comprehensive optimization of these parameters, an optimum efficiency of 21.59% is obtained. The research can provide a theoretical guidance for further performance improvement of the device with CZTS