Optimized active layer morphology via side-chain atomic substituents to achieve efficient and stable all-polymer solar cells

摘要

All-polymer solar cells (all-PSCs), consisting of conjugated polymers for both electron donors and acceptors, are promising photovoltaic candidates owing to their superior mechanical properties and long-term stability in addition to tunable light absorption and energy levels of the photoactive materials. One of the critical limitations to the device performance of all-PSCs is the non-ideal bulk-heterojunction morphology. Herein, we report the manipulation of active layer morphology for producing efficient all-PSCs based on a set of polymer donors (J52, J52-F, and J52-FS) with identical conjugated main chains but different side-chain atomic substituents. When blended with a state-of-the-art polymer acceptor NOE10, J52 provided a power conversion efficiency (PCE) of up to 8.7%, whereas J52-FS afforded a low PCE of 3.9%. The nano-spectroscopic imaging of the blend films revealed that the domain size in them is closely related to the device efficiency, and the highest PCE of the J52:NOE10 blend was contributed by its smallest domain size. The formation of different active layer morphologies was further explained by the Flory-Huggins interaction parameter. In addition, benefiting from the high miscibility of donors and acceptors, the J52:NOE10 devices achieved higher storage stability and thermal stability. These findings will aid in morphology optimization for high-performance all-PSCs.

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