Flexible Organic Ultraviolet Filters with Tunable Cutoff Wavelength for Enhancing Irradiation Stability of Organic Solar Cells
摘要
High-energy ultraviolet (UV) component of sunlight causing interfacial photochemical decomposition limits the operational stability of organic solar cells (OSCs). To maintain the mechanical flexibility of OSCs, flexible UV filters with tunable cutoff wavelength are desired to improve irradiation stability of devices under sun light. Here, we report the preparation of flexible UV filters by incorporating a benzotriazole-based UV absorber (UV326) and transparent polyimide (PI). The incorporation of UV326 in PI improves the stability of PI under UV radiation as well as enables spectrally selective UV management. The resulting flexile UV326@PI composite films exhibit excellent UV resistance with a tunable cutoff wavelength ranging from 370 nm to 400 nm. OSCs devices protected by the UV326@PI filter with a cutoff wavelength of 400 nm retained 82.6%±4.4% of their initial power conversion efficiency (PCE) after 400 h of continuous UV lamp irradiation (395 nm, 345 mW/cm2), whereas unprotected control devices degraded to 54.5%±4.2%. The flexible UV filters with tunable cutoff wavelengths could provide a possible route to enhance the photostability of flexible OSCs.