Molecular engineering of self-assembled monolayers for proton radiation-hardened flexible perovskite solar cells

The explosive growth of commercial aerospace and space computing demands lightweight, low-cost flexible solar wings, positioning flexible perovskite solar cells (FPSCs) as a key enabling technology. However, while the radiation hardness of perovskite absorbers is well-established, the degradation mechanism of organic hole transport layers (HTLs) under space radiation remains unexplored and represents a critical bottleneck. Here, we investigate the proton irradiation tolerance of self-assembled monolayers (SAMs) as HTLs with varying saturated alkyl chain lengths in inverted FPSCs under simulated low Earth orbit conditions. Following proton irradiation, 6PACz films exhibited the highest retention of surface morphology, minimal C–N bond cleavage, and reduced ionization damage among the investigated SAMs. As a result, 6PACz-based devices exhibited superior proton radiation hardness, retaining 90% of their initial efficiency (approximately 24%) after proton exposure. This exceptional stability is attributed to the maintenance of low interfacial defect densities and favorable energy level alignment. Our findings identify molecular chain engineering as a decisive strategy for eliminating the organic-layer bottleneck in next-generation space photovoltaics.