Dithienobenzimidazole-based semiconducting polymer for nonfullerene organic photovoltaics

Creation of thiophene-fused building unit is pivotal for development of high-performance organic semiconductors for organic electronics. Herein we report the design and synthesis of dithienobenzimidazole (DTBI) as a novel building unit for semiconducting polymers. The absorption spectrum of the DTBI-based polymer POBI was red-shifted by 20 to 60 nm relative to that of the polymers based on related building units, owing to the enhanced quinoidal character of DTBI. Photovoltaic cells based on POBI paired with a benchmark nonfullerene acceptor Y6 provided a power conversion efficiency of up to 6.3%. The photovoltaic performance of the POBI:Y6 blend film was characterized in terms of its crystallinity, morphology, and charge carrier transport properties.