Fluorescent Conversion Agent Embedded in Zinc Oxide as an Electron‐Transporting Layer for High‐Performance Non‐Fullerene Organic Solar Cells with Improved Photostability

Abstract Zinc oxide (ZnO) is widely used as an electron transporting layer (ETL) for organic solar cells (OSCs). Here, a low‐cost commercial water/alcohol‐soluble fluorescent conversion agent, sodium 2,2′‐([1,1′‐biphenyl]−4,4′‐diyldivinylene)‐bis(benzenesulfonate) (CBS), is incorporated into ZnO to develop a novel organic‐inorganic hybrid ETL for high‐performance OSCs. The photoinduced charge transfer from CBS to ZnO significantly improves the charge transport properties of ZnO, resulting in faster electron extraction and reduced charge recombination in OSC devices with ZnO:CBS ETLs. ZnO:CBS‐based devices exhibit higher power conversion efficiencies (PCEs) than their pure ZnO‐based counterparts, especially in devices with a thicker ETL, which is more suitable for roll‐to‐roll and large‐area module processing. Furthermore, the strong ultraviolet‐light absorption capability of CBS inhibits the photodegradation of the active layer, improving the photostability of ZnO:CBS based OSC devices. Therefore, this work provides a simple and effective strategy for realizing high‐performance OSCs with high PCE and good photostability, which can further facilitate the commercialization of OSCs.