High‐Efficiency Ternary Organic Solar Cells Based on the Synergized Polymeric and Small‐Molecule Donors

Despite the impressive progress that has been achieved for organic solar cells (OSCs) in recent years, challenges remain for OSCs due to the presence of the trade‐off between photovoltage and photocurrent that sets limitation on the performance enhancement of regular bulk heterojunction (BHJ) blends. Herein, a new small‐molecule (SM) donor, BPR‐SCl, with the deep‐lying highest occupied molecular orbital and strong crystallinity has been developed, which, as the third component, is synergized with PM6:Y6 host blend. The introduction of BPR‐SCl enhances molecular packing, exciton dissociation, as well as charge mobilities of ternary blends, yielding simultaneous enhancement of open‐circuit voltage, short‐circuit current density, and fill factor of ternary OSCs (TOSCs). As a result, an optimal power conversion efficiency (PCE) of 16.74% is obtained for TOSCs with 25 wt% BPR‐SCl, accounting for 10% and 70% improvements over those of pristine PM6:Y6 and BPR‐SCl:Y6 binary devices, respectively. Overall, herein, it is demonstrated that the design of SM donor as the third component is effective in achieving high‐performance TOSCs.