Cu2FeSnS4-based heterojunction solar cells with M O (M=Cu, Ni)-back surface field layers: Impact of defect density states and recombination

Copper-based chalcogenide quaternary semiconductors have emerged as promising candidates for next-generation photovoltaic (PV) devices, owing to their unique electronic and photonic properties coupled with environmentally friendly compositions. This study explores the potential of copper-based absorber materials, specifically Cu 2 FeSnS 4 (CFTS), as an absorber in heterojunction solar cells with Cu-/Ni-metal oxides back surface field (BSF) and SnS 2 buffer layers using the SCAPS-1D Simulator. Initially, we assess the performance of CFTS-absorber solar cells and compare the key photovoltaic metrics with those of other Cu-based semiconductors including CuIn x Ga (1- x ) Se 2 (CIGS), Cu 2 ZnSnS 4 (CZTS), Cu 2 CoSnS 4 (CCTS), Cu 2 NiSnS 4 (CNTS), Cu 2 BaSnS 4 (CBTS), Cu 2 MnSnS 4 (CMTS), to identify the most promising absorber. Subsequently, we optimize the layer properties, including active layer thickness, free-carrier concentration, bulk and interface defect density, and carrier recombination in potential CFTS. Further, we examine the impact of defects, and carrier recombination, including radiative, Shockley-Read-Hall (SRH), and Auger recombination. These detailed studies yield improved and competitive photoconversion efficiency, ( PCE ) of 27.31% (compared to 24.68%, without BSF) with open circuit voltage, ( V OC ) of 1.36 V, short-circuit current density, ( J SC ) of 22.28 mA/cm² and fill factor, ( FF ) of 90.47% for Cu 2 O, whereas the PCE of 26.97% with V OC of 1.07 V, J SC of 28.82 mA/cm² and FF of 86.91% for NiO x BSF layer in Au/Mo/BSF(Cu 2 O and NiO x )/CFTS/SnS 2 /ZnMgO/ZnO:Al/Pt configurations under optimized conditions. The enhanced charge separation and carrier collection efficiencies reveal the strong potential of CFTS absorber heterostructures with Cu 2 O/NiO x , SnS 2, and bi-layer ZnMgO/ZnO:Al as BSF, buffer, and window layers, repectively, providing insights and resources for developing high-efficiency CFTS-based photovoltaic devices.