Improving the efficiency of ZnO/WS2/CZTS1 solar cells using CZTS2 as BSF layer by SCAPS-1D numerical simulation

Abstract

With a high absorption coefficient and tunable bandgap CZTS (Copper Zinc Tin Sulfide) makes it suitable for photovoltaic applications. Present paper deals with the simulation and modeling of CZTS-based solar cells using tungsten disulfide (WS2) as the buffer layer and CZTS2 as the back surface field (BSF) layer to study the performance of the solar cell. Considering different physical and geometrical parameters such as thickness, acceptor density, interfacial defect density, and metal contact work functions the device calibration has been done. The temperature is varied from 300 K to 400 K to study the impact on device performance. The C-V and 1/C2 plot is presented to calculate the built-in voltage for the device. The series (Rs) and shunt (Rsh) resistance of 1 and 106 ohm.cm2 were kept throughout the simulation. The optimized thickness for the absorber, BSF, buffer, and window layers are 800 nm, 140 nm, 30 nm, and 90 nm respectively. The obtained results are validated using the experimental results available in the literature. Varying the values of different parameters, the optimal efficiency of 26% was reported in this work. Contrary to conventional solar cells, which contain expensive and toxic elements, WS2 may be a good option as a buffer layer in CZTS solar cells.