Hole Transport Layer-Free CsSnI ₃ ‑Based Perovskite Solar Cells with WS ₂ Electron Transport Layer: Design,...

Perovskite solar cells (PSCs) have garnered significant attention due to their outstanding optoelectronic properties and ease of fabrication. However, their commercialization is hindered by high costs and stability issues associated with the Hole Transport Layer (HTL) and the high cost of back contacts. In this study, a novel, cost-effective, HTL-free PSC structure using a lead-free CsSnI₃ absorber and WS₂ electron transport layer (ETL) is designed and optimized using SCAPS-1D simulation. The device performance was enhanced by systematically optimizing key parameters, including layer thickness, doping concentration, defect density, and series/shunt resistance. The optimized cell, utilizing a Nickel (Ni) back contact, achieved a Power Conversion Efficiency (PCE) of 26.08%, with an open-circuit voltage (V_oc) of 0.94 V, a short-circuit current (J_sc) of 34.84 mA/cm² and a fill factor (FF) of 79.89%. This design offers a highly efficient, nontoxic, and economically viable alternative by replacing traditional, expensive HTL/metal contact combinations (>500 euros/g) with Ni, which costs only ∼2.23 euros/g.