SnS BSF introduction enables efficient CZTSSe solar cells: modeling and analysis

Abstract Kesterite, Cu 2 ZnSn(S,Se) 4 (CZTSSe) has emerged as a promising photovoltaic material for developing solar cells. However, the carrier recombination losses at heterointerfaces in the CZTSSe device structure and the weakened absorber layer conductivity induce open circuit voltage ( V oc ) deficit and efficiency loss. Herein, SnS was introduced as back surface field (BSF) layer at CZTSSe/Mo back heterointerface to suppress interfacial recombination. The CZTSSe based solar cell with the configuration of ITO/i-ZnO/CdS/CZTSSe/SnS/Mo has been modelled using wxAMPS software. The device performance potential of the proposed solar cell was examined by varying several critical parameters (including thickness, carrier concentration and bulk defects of CZTSSe absorber layer, thicknesses and carrier concentrations of CdS buffer and SnS BSF layers, interface defect densities at heterointerfaces and back contact material work function). It is revealed that the insertion of SnS BSF between the absorber layer and the back contact metal minimizes the carrier recombination, thus raising the conversion efficiency. Through the device simulation and performance optimization, the device delivered the conversion efficiency of 25.01%. These findings reported in this study provide some insights and guidelines for fabricating highly efficient and environmentally friendly thin film solar cells.