Design and synthesis of star-shaped non-fullerene acceptors based on triarylamine core for organic photovoltaic applications

Abstract Non-fullerene acceptors were synthesized with triphenylamine (TPA) and 9-phenylcarbazole core functionalized with oxindole moiety as well as electron accepting groups such as cyano and trifluoromethyl groups leading to precisely tuned molecular electronic structures and intermolecular arrangements. This approach maintained high thermal stability and excellent electron mobility while optimizing optoelectronic properties, providing a novel strategy for developing organic photovoltaic materials. LUMO levels of three receptors are comparable to PC61BM. The decomposition temperatures of all three acceptors exceeded 380°C under N2 flow, indicating the exceptional thermal stability. Notably, the acceptor consisting of TPA core with three oxindole moieties exhibited the red-shifted and intense UV-vis absorption spectrum and the narrowest optical bandgap (Egopt = 2.14 eV). Furthermore, the higher electron mobility was observed compared to analogues with 9-phenylcarbozle unit. The power conversion efficiency (PCE) of the device based on TPA core acceptor and regio-regular poly(3-hexylthiophene) surpassed those of the devices based on the other two acceptors.