Perovskite Solar Cell Efficiency and Thermal-Stability Enhancement via Interfacial Engineering: A Numerical Analysis

The marketable viability of perovskite solar cells (PSCs) is currently hindered by challenges related to interfacial charge-carrier extraction and thermal degradation. This study presents a comprehensive finite element method (FEM) analysis using COMSOL Multiphysics to evaluate the efficacy of bi-layer electron transport layer (ETL) engineering in addressing these limitations. We developed a coupled optical–electrical model to investigate three planar architectures: a conventional TiO2-based reference device, a TiO2/SnO2 bi-layer configuration, and a TiO2/SnO2:Fe (iron-doped) bi-layer device. Simulation results under AM1.5G illumination reveal that the bi-layer configurations significantly enhance optical absorption across the visible spectrum (350–700 nm) compared to the single-layer counterpart. The incorporation of Fe-doped SnO2 resulted in optimized energy band alignment, creating a favourable conduction band offset that facilitates electron extraction. Consequently, the TiO2/SnO2:Fe device achieved a peak power conversion efficiency (PCE) of 18.3% at 300 K, outperforming the undoped bi-layer (18.0%) and the reference device (17.5%). Furthermore, thermal stress simulations indicated that the Fe-doped architecture exhibits superior stability, maintaining a PCE of 12.8% at 440 K compared to 12.3% for the reference. This enhanced performance is attributed to the passivation of interfacial defects and the formation of a stronger built-in electric field at the ETL/absorber junction, validating the strategic doping of metal oxides as a robust pathway for high-efficiency, thermally stable perovskite photovoltaics.