Abstract
ABSTRACT Understanding the radiation tolerance of charge‐transport layers is essential for the reliable operation of organic solar cells (OSCs) in space. Here, we compare the response of conventional and inverted PM6:Y6 OSCs to extreme 140 keV pulsed proton irradiation at a fluence of 10 12 protons cm −2 , with particular emphasis on transport‐layer‐dependent degradation. Although both architectures show similar initial power‐conversion efficiencies, the inverted devices retain substantially higher photovoltaic performance after irradiation than the conventional counterparts. Loss analysis reveals that irradiation increases non‐radiative V OC losses and series‐resistance‐related fill‐factor losses in both architectures, with markedly stronger degradation in conventional devices. X‐ray photoelectron spectroscopy indicates irradiation‐induced modification of nitrogen chemical states in PDINN and defect‐related oxygen states in ZnO. Combined with the voltage‐impedance spectroscopy analysis, these results are consistent with significantly stronger radiation‐induced interfacial trap formation in the conventional architecture than in the inverted one. Post‐irradiation thermal annealing partially restores device performance, with much more effective recovery in inverted OSCs. Overall, the results show that transport‐layer/interfacial design plays a decisive role in radiation tolerance and identify inverted PM6:Y6 OSCs as the more promising architecture for ionizing radiation environments.