Numerical simulation to optimize the photovoltaic performances of Cu2ZnSnS4 solar cell with Cu2NiSnS4 as hole transport layer

Abstract

Cu₂ZnSnS₄ (CZTS) has been taken as an encouraging absorber material for photovoltaic (PV) device applications due to its earth-abundant composition, favorable bandgap, and non-toxicity. However, the recombination losses at both front and back interfaces in the heterojunction CZTS solar cells provide poor efficiency and open-circuit voltage (V_oc). In this study, we have designed and investigated heterojunction CZTS-based solar cell employing Cu₂NiSnS₄ (CNTS) as hole transport layer (HTL) and tungsten disulfide (WS₂) as buffer layer. A novel solar cell structure of Ni/CNTS/CZTS/WS₂/FTO/Al has been designed numerically by utilizing the one-dimensional solar cell capacitance simulator (SCAPS-1D). At first, we have verified an experimental structure (Mo/CZTS/CdS/ZnO) with conversion efficiency of 8.38 % without HTL numerically with the help of the SCAPS-1D simulator for the validation purposes. A comparison of the PV performances among different HTLs is provided. It is revealed that the addition of HTL at rear side of the CZTS cell minimizes the carrier recombination, thus improving the device outputs. Also, the lower lattice mismatch between the proposed CNTS HTL and CZTS absorber compared to other HTLs further results in better performances. In addition, a ‘spike like’ band orientation at the CZTS/WS₂ interface helps to increase PV outputs by reducing the carrier recombination loss. The output of proposed CZTS heterojunction TFSC is further examined by changing different parameters including thickness, doping concentration, bulk and interface defect densities, temperature, cell resistances, and metal work function. In this work, an optimized thickness for CZTS absorber is found to be 1.0 μm for the cost-effective PV device. A maximum efficiency of 30.26 % including V_oc of 1.08 V, short-circuit current density (J_sc) of 31.75 mA/cm², and fill-factor (FF) of 88.04 % is achieved numerically. Therefore, these findings will help to researchers for designing Cd-free, low-cost, environmentally friendly, and highly efficient CZTS heterojunction TFSC.