Influence of SnS and Sn2S3 based BSF layers on the performance of CZTSSe solar cell

Thin-film solar cells are widely used nowadays to minimize the cost of the device. CZTSSe (copper zinc tin sulfide selenide) is a thin film material used in solar cells due to its high absorption coefficient, greater stability and cheaper production process. However, the achieved efficiency of CZTSSe based solar cell is only ~12%. The surface recombination at the back contact is one of the major hindrances in these devices. Therefore, in this work, to minimize the back-surface recombination, the back-surface field (BSF) layers are introduced. In this regard, SnS (tin sulfide) and Sn2S3 (tin (IV) sulfide) are used as BSF. Further, to analyze the impact of BSF, a comparative study between conventional and BSF layer-based devices has also been done. The results show a rise in the efficiency from 12.57% to 16.34% and 12.57% to 17.04% with the introduction of SnS and Sn2S3 based BSF layers, respectively. The improvement is attributed to the reduction in the recombination of carriers at the back surface of the device. It has been observed that the device with the BSF layer of Sn2S3, the maximum open-circuit voltage (Voc) is 0.59V, short circuit current density (Jsc) is 37.68 mA/cm−2 and fill factor (FF) is 76.46%. All the simulation results are validated using energy band diagram (EBD) of the devices.