High-performance numerical modeling of toxic-free CZTS solar cell structure

Abstract

A systematic numerical study of a toxic-free CZTS solar cell model based on the ZnO buffer layer is numerically investigated and analysed using the SCAPS-1D simulation platform. The proposed toxic-free CZTS model exhibits an improvement in the current density (Jsc) of about 1.41 mA/cm2 and 6.33% in quantum efficiency (QE) compared to the conventional toxic structure. The simulation results of the eco-friendly model reveal an optimum efficiency of about 19.96% at a bandgap energy of 1.42 eV and with absorber thickness as low as 1600 nm. It has been observed that increasing the doping level from 1015 cm−3 to 1018 cm−3 results in an efficiency enhancement of about 2.5%. To maintain the high-performance of the device, the ZnO buffer layer must be as thin as 100 nm with a bandgap energy of 3.3 eV. The increase in buffer layer thickness above 100 nm leads to deterioration in the device performance. This might be ascribed to the increase of the recombination rate due to the increase of carrier diffusion length away from the junction at thicker ZnO thicknesses.