Passivation-Driven Suppression of Ion-Migration-Induced Hysteresis in Perovskite Solar Cells

Ion migration and defect-assisted nonradiative recombination are major causes of current–voltage (J–V) hysteresis and operational instability in tin-based perovskite solar cells (PSC). In this work, a dynamic ion-migration model was developed for a conventional n–i–p device based on a methylammonium tin iodide (MASnI₃) absorber to investigate the effects of scan rate, mobile-ion density, ionic diffusivity, activation energy, and surface passivation. All reported device responses and passivation-dependent trends were obtained from the proposed simulation framework and interpreted using experimentally relevant diagnostic parameters. At an ion density of 10¹⁶ cm^–3 and a scan rate of 100 mV s^–1, methylammonium chloride (MACl) reduced the hysteresis index from 8.30% to 1.00%, corresponding to 87.9% suppression. Lead(II) chloride (PbCl₂) increased the ion-migration activation energy from 0.35 to 0.50 eV, decreasing the diffusion coefficient from 10^–10 to 3.0 × 10^–13 cm² s^–1. The combined MACl + PbCl₂ treatment provided the broadest low-hysteresis operating window. Passivation also reduced the relative trap density by approximately 75%, increased electroluminescence efficiency from 2.5% to 8.6%, extended carrier lifetime from 1200 to 3500 ns, enhanced mobility from 0.5 to 45 cm² V^–1 s^–1, and increased quasi-Fermi-level splitting (QFLS) from 1.12 to 1.25 V. These findings demonstrate that simultaneous control of ionic defects and interfacial recombination is essential for stable and efficient tin-based PSC.