Numerical simulation of Cu2ZnSnS4 based solar cells with In2S3 buffer layers by SCAPS-1D

The performance of the Cu2ZnSnS4 based solar cell is investigated using a simulation program called Solar Cell Capacitance Simulator (SCAPS). The cell structure is based on Cu2ZnSnS4 (CZTS) compound semiconductor as the absorber layer, n-doped and un-doped (i) zinc oxide as the window layer, In2S3 as the buffer layer.We study the influence of the defect density, carrier density, thickness of the CZTS absorber layer, working temperature, In2S3 buffer layer thickness and its carrier density on the cell performance. The simulation results illustrate that the optimal layer thickness is from 2500 to 3000 nm for the absorber layer, and that in the range of 20 to 30 nm for the buffer layer. Besides, controlling the CZTS defect density under 1 × 1013 cm-3 is very necessary for high efficiency CZTS cells. The increased working temperature has a strong influence on the solar cell efficiency and the temperature coefficient is calculated to be about -0.17%/K. An optimal photovoltaic property has been achieved with an efficiency of 19.28% (with Jsc = 23.37 mA/cm2, Voc = 0.958 V and FF = 86.13%). All these simulation results will give some important guides for feasibly fabricating higher efficiency CZTS solar cells.