Direct C–H arylation-derived low crystallinity guest acceptor for high efficiency organic solar cells†

Abstract

The majority of host/guest materials used in organic solar cells (OSCs) are currently synthesized via the Stille reaction, which suffers from poor atom/step economy, low cost-effectiveness, and environmental risks. Therefore, organic photovoltaic materials synthesized through low-cost and green methods are highly required. Here, an A–D–D–A type guest acceptor D-IDT was designed and synthesized using a tin-free direct C–H activation strategy and introduced into the classical D18:BTP-eC9 host system. Compared to the A–D–A type guest acceptor S-IDT, the D-IDT shows a greater π-conjugation but much weaker intermolecular interactions. Its low crystallinity results in good miscibility with the host acceptor BTP-eC9, which effectively promotes earlier assembly of BTP-eC9 and faster aggregation transition. This allows the formation of a smaller phase separation in the active layer, resulting in efficient exciton dissociation and charge transport. Moreover, the voltage loss of the OSC device reduces by 18 mV when D-IDT is incorporated into the binary system. As a result, the efficiency of the D-IDT-controlled device is increased to 19.92% compared to the device with S-IDT (17.66%). This work provides valuable guidelines for the exploration of guest materials via the C–H activation reaction, while controlling the crystallization kinetics to fine-tune the assembly behavior of the host acceptor.