Halogen-Acupuncture Stabilization of Pure-Iodide Wide-Bandgap Perovskites for Efficient and Stable Solar Cells under Simulated Low-Earth-Orbit Cycling

Pure-iodide wide-bandgap (WBG) perovskites are promising top-cell absorbers for tandem photovoltaics, benefiting from their intrinsic immunity to the halide phase segregation that plagues mixed-halide counterparts. However, their practical deployment, particularly in space, is severely impeded by iodine migration and iodine-loss-induced degradation. Here, we propose a halogen-acupuncture-enabled iodide anchoring strategy, in which halogen-bond interactions act as site-specific “molecular needles” to immobilize iodide species. By introducing 2-halonaphthalene molecules (2XN, X = Cl, Br, I), strong halogen bonding increases the formation energy of iodine vacancies and inhibits iodine-ion-related degradation. Among them, 2-iodonaphthalene (2IN) delivers the most pronounced stabilization effect while concurrently regulating crystallization kinetics, producing films with enhanced crystallinity, reduced residual strain, and superior electronic quality. Consequently, the optimized pure-iodide WBG perovskite solar cells deliver a champion power conversion efficiency of 22.41% with reduced hysteresis, while 1 cm² devices achieve a high efficiency of 21.41%. More importantly, the 2IN-treated perovskite solar cells (PSCs) exhibit remarkable durability under both light on-off cycling and simulated low-Earth-orbit (LEO) light-thermal cycling, retaining 80% of the initial efficiency after 135 LEO cycles between 240 and 330 K. These results highlight the potential of this iodide-anchoring strategy for space photovoltaic applications.