Numerical simulation of perovskite/Cu2Zn(Sn1-x Gex)S4 interface to enhance the efficiency by valence band offset engineering

In this paper a perovskite solar cell which consists of an inorganic hole transporting layer is studied using a SCAPS simulator. The primary structure of investigated solar cell is FTO/TiO2/MAPbI(3)/Spiro-OMeTAD/Ni which has PEC of 21.30%. The Cu2Zn(Sn1-x Ge-x)S-4 compound is good candidate as HTL in perovskite solar cells due to tunable band gap with different Ge/(Ge + Sn) ratios. The band gap was modulated from 1.5 for Cu2ZnSnS4 to 1.95 for Cu2ZnGeS4 with appropriate valence band offset engineering at the MAPbI(3)/Cu2Zn(Sn1-x Gex)S-4 interface. The solar cell performance was optimized by varying the Ge concentration, leading the PCE 20.86%. The data suggested that maximum efficiency is observed for Ge concentration x = 0.8. It is also observed that an appropriate VBO (0.20eV) with CZT(0.2)G(0.8)S hole transporting layer can be achieved. (C) 2019 Elsevier B.V. All rights reserved.