Numerical Modeling and Parameter Optimization of Kesterite Based Thin Film Solar Cell by SCAPS 1D

A non-toxic and plentiful semiconductor compound, copper-zinc-tin-sulfide (Cu2ZnSnS4) has a high absorption coefficient (104 cm-1) and an ideal band gap (1.3-1.5eV). Using SCAPS 1D software, the CZTS solar cell is first modelled in this work. Layer parameters are then improved and cell characteristics such as Voc, Jsc, FF, and η are recorded for optimal solar cell performance and compared with experimental findings. The cell structure simulated in this work is CZTS/CdS/i-ZnO/ZnO: Al. In this structure CZTS works as an absorber layer, CdS as buffer layer, i-ZnO as window layer and ZnO:Al as Transparent conducting oxide (TCO) for transport of electron. We have optimized the CZTS layer's thickness, Bang Gap of CZTS (Eg), CdS thickness, Acceptor carrier density (Na) for absorber layer and donor carrier density for buffer layer. This work also examines the impact of working temperature. The optimized values of CZTS thickness, band gap and acceptor carrier density for the above structure came out to be 2.5μm, 1.45eV and 1x1016 /cm3 respectively. The optimized values of thickness and donor density of the buffer layer found to be 75μm and 1x1018 /cm3. The optimum temperature is 300K. By using these optimized parameters in the SCAPS 1D software, the best performing solar cell in this work produced Voc= 0.44V, Jsc= 45.87 mA/cm2, FF=63.44% and η= 12.90%. These results are then compared with the experimental results. The experimental result gave the efficiency of about 6.2% when CZTS thin films are grown by co-sputtering for the same cell structure.