Unlocking the Potential of WS₂ as an Electron Transport Layer in Flexible and Lead-Free Methylammonium Tin Iodide-Based Perovskite Solar Cells: A Comprehensive Defect Study Using the SCAPS-1D Framework

The hazardous lead component in perovskite solar cells (PSCs) has raised environmental concerns, hindering commercialization. A simulation study is performed using a lead-free, eco-friendly ITO/WS₂/MASnI₃/NiO/Au PSC structure using SCAPS-1D software. This structure utilizes tungsten disulfide (WS₂) as an electron transport layer (ETL), methylammonium tin iodide (MASnI₃) as an absorber layer, and nickel oxide (NiO) as a hole transport layer (HTL). The study found the optimized bandgap for the WS₂ layer to be 1.6 eV, with an optimized thickness of 0.5 µm. The highest permissible defect density in the WS₂ interface is 10¹⁵ cm⁻³, while in the WS₂/MASnI₃ interface, it is lower at 10¹¹ cm⁻³. High defect density reduces the photo conversion efficiency (PCE) of the PSCs. The simulated PSC structure has a lower activation energy of 1.08 eV, indicating an interface recombination center. The optimized device achieved a PSC efficiency of 28.15 %, a V_OC value of 0.96 V, and a fill factor (FF) of 83.36%. Notably, the PCE increased to 28.58% at a lower temperature of 280 K. This breakthrough underscores the potential of WS₂ as an efficient ETL in eco-friendly PSCs for non-toxic renewable energy solutions.