Sensitivity-Based Performance Optimisation of a Lead-Free Formamidinium Tin Iodide (Fasni3) Perovskite Solar Cell Using Scaps-1d Simulation

This work presents a design and simulation framework for the multi-parameter optimization of a lead-free Perovskite Solar Cell (PSC) with an FTO/CeO2/FASnI3/CuI structure. It focuses on the device parameters that influence operational stability. Using the Solar Cell Capacitance Simulator One-Dimension (SCAPS-1D) (version 3.3.12), the study first verified the baseline performance of the device. Six parameters, previously optimized for efficiency, were re-evaluated and categorized into fixed design parameters set during fabrication and those susceptible to drift through known FASnI3 degradation pathways. Normalized sensitivity coefficients were then calculated from the simulation sweeps. The results showed a baseline Power Conversion Efficiency (PCE) of 22.04%, an open-circuit voltage (Voc) of 0.9843V, a short-circuit current density (Jsc) of 26.01 mA/cm², and a fill factor (FF) of 86.12%. Following multi-parameter optimisation of bandgap, absorber thickness, and back-contact work function, the device achieved an optimised PCE of 24.85%, with a Voc of 0.9307 V, a Jsc of 30.65 mA/cm², and an FF of 87.10%. Sensitivity analysis revealed that electron affinity is the most influential factor on PCE, with roughly 19 percentage points per eV, followed by acceptor density (about 0.57 percentage points per decade) and defect density (around 0.20 percentage points per decade). The study highlights interfacial electron affinity control as a priority for enhancing device stability, since among the parameters examined PCE proved most sensitive to drift in electron affinity; defect density, however, remains the parameter most likely to drift in practice through the known Sn²⁺ oxidation pathway.