Sustainably Synthesized Plasma Encapsulants for Organic Solar Cells With Enhanced Stability Under Harsh Moisture and UV Exposure

Organic solar cells (OSCs) have achieved rapid efficiency advances; however, limited operational stability remains a key bottleneck for their scalable production and real‐world deployment. Here, we develop a green, solvent‐free encapsulation strategy using radio‐frequency (RF) plasma‐polymerized thin films derived from Citrus sinensis (orange oil) and evaluate protection under extreme stress. Two continuous‐plasma conditions (70 and 80 W) produced the most effective barrier layers. Under 8 h of water‐droplet soaking, encapsulated PM6:Y6 devices retained ~70%–80% of their initial power conversion efficiency (PCE), while nonencapsulated devices failed rapidly. Partial performance recovery after water soaking was observed following mild glovebox annealing, indicating that a portion of the moisture‐induced loss is reversible. Moreover, encapsulated OSCs retained >60% of original PCE under continuous UV irradiation (352 nm) for up to 5 days, while reference devices degraded within the first day. Film analyses (UV–vis/Tauc, FTIR, XPS, SEM, and WCA) indicate hydrocarbon‐rich networks with minor oxygen incorporation, and UV‐induced oxidation that correlates with reduced hydrophobicity. Overall, orange‐oil plasma–polymer encapsulation provides a scalable, adhesive‐ and solvent‐free route to improved OSC durability under moisture and UVA stress.