Numerical Investigation of Defect–Temperature Effects on the Operational Reliability of Lead-Free FASnI₃ Perovskite Solar Cells

Abstract

The long-term performance of perovskite solar cells is limited by thermal stress and defect-assisted recombination, which accelerate degradation during operation. This study presents a reliability-oriented modeling approach using defect–temperature phase diagrams to identify stable operating conditions for lead-free FASnI₃ perovskite solar cells using SCAPS-1D. Simulations were conducted over an operating temperature range of 300–400 K and a bulk defect density of 1 × 10¹⁰ to 1 × 10¹⁷ cm⁻³. Normalized power conversion efficiencies were used to construct reliability phase diagrams, and sensitivity coefficients were determined to assess their relative impact on performance. The simulated device maintained stable performance across temperatures when bulk defect density remained low. However, performance declined rapidly once defect density exceeded ~1 × 10¹⁴–1 × 10¹⁵ cm⁻³ due to enhanced trap-assisted recombination. The reliability maps categorized operating conditions into four regions—Robust, Reliable, Critical, and Failure—showing that variations in defect density affect performance significantly more than operating temperature. The proposed framework offers a practical method for evaluating defect tolerance, setting safe thermal limits, and designing durable, long-lasting lead-free perovskite solar cells for sustainable energy deployment.