Ambient‐Processed Organic Solar Cells Achieving Nearly 20.5% Efficiency and Industrially Viable Environmental Stability

The ability to process organic solar cells (OSCs) in ambient air is a critical prerequisite for industrial-scale production, as it obviates the need for a high-cost inert atmosphere. However, state-of-the-art cathode interlayers (CILs) typically require strongly hydrophilic groups to ensure adequate solubility and feasible work function, which inevitably render them susceptible to moisture and oxygen in air, thereby compromising the photovoltaic performance. In this study, we introduce diethoxysilane (DEES) and its derivatives into the high-performance CIL PNDIT-F3N, where they hydrolyze and condense under ambient conditions to form a cross-linked, hydrophobic Si─O─Si moisture-protective network. Moreover, DEES incorporation effectively reduces the activation energy for electron transport of PNDIT-F3N and suppresses detrimental aggregation, thus optimizing charge transport and extraction efficiency. As a result, the DEES-modified OSCs achieve record efficiencies of 20.48% under 50% relative humidity (RH) and 20.22% under 80% RH, each representing one of the highest values reported for air-processed devices. More importantly, the unencapsulated DEES-modified devices exhibit exceptional operational stability, averaging 2270 h to 80% of initial efficiency under continuous visible-LED illumination (photocurrent equivalent to AM1.5G, 45%-55% RH). This work provides a facile and generalizable strategy to enhance moisture tolerance of OSCs, advancing the industrial production and commercial viability of air-processed organic photovoltaics.