Cost-Effective Nickel Plasmonic Double-Ring Arrays for Enhanced Light Trapping in Lead-Free CsInCl₃ Perovskite Solar Cells

Lead-free all-inorganic CsInCl₃ perovskites offer eco-friendly photovoltaic properties but suffer from weak visible absorption. We introduce cost-effective, stable nickel–iron (Ni–Fe) plasmonic double-ring arrays at the SnO2/CsInCl₃ interface and optimize the device using finite-difference time-domain (FDTD) simulations coupled with charge-transport modeling. By tuning the Ni:Fe composition, we broaden localized surface plasmon resonances across the visible spectrum, achieving up to 40% enhancement in optical absorption at 520 nm over the pristine device. The optimized Ni–Fe alloy double-ring array yields a short-circuit current density (Jsc = 18.5 mA/cm²) and a power conversion efficiency (PCE = 14.2%), representing a 52% improvement over the reference structure. Ni–Fe demonstrates superior thermal stability with negligible PCE degradation over 1,000 hours at 85 °C, outperforming both pure Ni and Ag. This establishes Ni–Fe alloys as scalable, low-cost plasmonic materials for commercially viable lead-free perovskite photovoltaics