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

ABSTRACT 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 cm 2 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.