Combined DFT and SCAPS-1D Investigation of Thermodynamic, Mechanical, and Electronic Properties of Iron-Doped SnO₂ toward Perovskite Solar Cell Applications

This work explores Fe-doped SnO₂ as an efficient electron transport layer for lead-free tin-based perovskite solar cells. Using first-principles DFT, the electronic, mechanical, and thermodynamic properties of pristine and Fe-doped SnO₂ were examined. Results show that 25% Fe doping enhances performance by reducing the band gap from 2.991 eV to 2.793 eV, improving carrier effective mass and mobility, and increasing mechanical stability. These changes also promote better band alignment with the CsSnI₃ absorber. Mechanical properties analysis reveals stronger mechanical stability for 25 % Fe–SnO₂. SCAPS-1D device simulations further confirm reduced recombination and improved electron extraction, raising the PCE from 10.83% to 17.54%. Overall, 25% Fe doping is identified as optimal, making Fe–SnO₂ a promising, stable, and eco-friendly ETL for high-performance perovskite solar cells.