Siloxane as Humidity‐Resistant and Stabilizing Additive for Ambient‐Processed Organic Solar Cells

Abstract High‐performing organic solar cells (OSCs) being processed in ambient conditions and possessing long‐term stability are desired toward commercialization. Here, resultantly bifunctional additive is proposed for organic active layer, which can greatly enhance humidity endurance during the air‐processing of the active layer and device stability in the meantime. Intriguingly, with 1% octamethyltrisiloxane (3Si) as the additive, casting PM6:L8‐BO active layer even in 90% relative humidity (RH) air could show comparable efficiency to that in N 2 condition. Furthermore, the 3Si‐processed active layers also display remarkably enhanced thermal and light stabilities in conventional OSCs. After thermal aging at 85 °C for 1000 h and simulated solar light aging with UV band at 100 mW cm −2 and 55°C for 1000 h, the 3Si‐processed PM6:L8‐BO binary OSCs maintain 91.6% and 86.1% of the initial efficiency, leading to final averaged efficiencies of 16.17% and 15.42%, respectively. The results represent the most stable OSCs based on additive strategy. The universality of siloxane as a humidity‐resistant and stabilizing agent is also confirmed with other active layer systems, paving a way for broader application of the bifunctional additive.