A new non-fullerene acceptor based on an asymmetric electron-deficient core for indoor organic photovoltaic cells

Extending the number of fused aromatic rings in & pi;-conjugated materials has proven to be an effective strategy to tailor the electronic, optical, and structural properties. In this work, the structure of the well-known Y6 was modified and a new asymmetric non-fullerene acceptor BIID was developed for organic photovoltaics. BIID was found to show a slightly blue-shifted absorption spectrum compared with Y6 in solid thin films. A high efficiency of 19.5% was achieved by using an BIID:PM6 bulk heterojunction blend film in a 1 cm2 device under indoor LED light, while an efficiency of 17.6% was achieved from the Y6:PM6 blend under the same conditions. Several characterization techniques were applied to study the structure-property relationships, and it was found that the BIID:PM6 blend has less trap-induced recombination, which led to a much higher open circuit voltage and higher device efficiency. With numerous possibilities for further structural optimization, such as attaching various substituents to the central electron-deficient core, BIID is considered to be a class of promising non-fullerene acceptors for indoor organic photovoltaics.