Simulation of ion migration in perovskite solar cells at elevated temperature and voltage levels

A coupled modeling approach based on Sah-Noyce-Shockley theory has been developed to simulate the ion migration in perovskite solar cells under elevated temperature and bias levels. The model considers the migration of cations (MA⁺) and anions (I⁻) across the structure of a MAPbI₃ solar cell (TiO₂/Perovskite/Spiro) demonstrating how at elevated temperature and applied voltage levels, the ion can migrate with different speed and the ion concentration profiles can influence the device performance parameters. Results reveal that low-energy ions migrate rapidly toward the interfaces under forward or reverse bias, with cation concentrations reaching ∼10²⁰ cm⁻³ at the TiO₂/perovskite interface under –1 V and anion concentrations with maximum at perovskite/spiro interface under +1  V. Deep defect levels (E_t = 1.4  eV) act as ion pinning centers, limiting cation migration compared to shallower traps (E_t = 0.7  eV), especially at high temperatures. Voltage has a stronger effect on ion migration compared to temperature. Thermal stress induces uniformity in ion distribution, whereas the bias causes more pronounced migration. Our modeling results agree well with experimental data from literature. Temperature elevation from 300  K to 500  K leads to enhanced ion migration, increasing bulk concentrations by two orders of magnitude (∼10¹² to ∼10¹⁴ cm⁻³) while preserving maximum accumulation at the interfaces. Carrier transport modeling based on Sah-Noyce-Shockley theory indicates that ion accumulation at interfaces increases the interface recombination and reduces the open-circuit voltage and the fill factor.