Boosting the efficiency of organic solar cells based on a highly planar π-conjugated solid additive working as the sensitizer

Solid additives have been demonstrated as a simple and effective approach to improve the performance of organic solar cells (OSCs). The exploitation of excellent solid additive is an important aspect to obtain efficient OSC. This research designs and synthesizes a novel solid additive IDT(BDT-IC)2 as the sensitizer for OSCs. The IDT(BDT-IC)2 is an A-π-d-π-A type molecule, which possesses a highly planar π-conjugated structure. This molecule exhibits a complementary light absorption with suitable energy levels, which meets the requirement of a qualified sensitizer. It helps to enhance the external quantum efficiency spectrum of the device. Thus, an increased photocurrent is achieved. The addition of IDT(BDT-IC)2 promotes the formation of a cascade energy level alignment and tunes the miscibility of the active layer. Both the exciton dissociation and electron transportation are improved, which enhances the fill factor. As a result, the average power conversion efficiency (PCE) of the PM6:Y6 OSC is increased from 15.75 % of the control device to 16.34 % by incorporating merely 0.25 wt% of IDT(BDT-IC)2. And the highest PCE with a value of 16.70 % is obtained. This research offers a facile and effective strategy for highly efficient OSCs by applying solid additive as the sensitizer.