Surface Passivation Suppresses α-Particle-Induced Trap Formation in Perovskite Solar Cells for Space Applications

Abstract α-Particles represent the second most abundant ionic species in space radiation, yet their specific degradation mechanisms and mitigation strategies in perovskite solar cells (PSCs) remain unquantified. Here, we evaluate the degradation of PSCs under 2.5 MeV α-particle irradiation and investigate the protective role of a propane-1,3-diammonium iodide (PDAI2) surface passivation. Following irradiation, PDAI2-passivated target devices retain 80% of their initial efficiency (20.22%), whereas control devices retain 60% (19.13%). Performance losses were dominated by fill factor degradation. X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy indicate that while α-particle induces partial organic cation loss and morphological variations, the primary crystalline phase is preserved without secondary phase decomposition. Capacitance–voltage, impedance spectroscopy, and Kelvin probe force microscopy confirmed that performance losses originate predominantly from photoactive trap states generated at the perovskite surface and interface, which increase space-charge density and transport resistance. Diammonium cations coordinate undercoordinated surface sites and crosslink organic cations, preventing radiation-generated point defects from stabilizing into transport-impeding traps. These findings establish surface defect chemistry control as a key strategy against high linear energy transfer (LET) ion radiation in space photovoltaics.