Rylene‐Fullerene Hybrid an Emerging Electron Acceptor for High‐Performing and Photothermal‐Stable Ternary Solar Cells

Molecular carbon imides, especially extended perylene diimides (PDIs) have been the best wide-band-gap nonfullerene acceptors. Despite their excellent photothermal/chemical stability, flexible reaction sites, and unique photoelectronic properties, there is still a lack of fundamental understanding of their molecular characteristics as a third component. Here, generations of PDIs with distinctive molecular architecture, are deliberately screened out as the third component to PM6:Y6. Only a rylene-fullerene hybrid, S-Fuller-PMI, surprisingly boosts the fill factor (FF) of ternary organic solar cells (OSCs) to 0.77 from 0.72 for PM6:Y6 binary ones, and therefore the power conversion efficiency (PCE) of ternary cells is enhanced from 15.3% to 16.2%. Compared with highly-flexible rylene dimer and rigid multimer, S-Fuller-PMI exhibits higher electron mobility, favorable surface tension, and, therefore tailored compatibility with Y6. These formed Y6:S-Fuller-PMI alloys play as a morphological controller to improve charge separation and transport process. Simultaneously, the suppressed photothermal-induced traps, along with inherent enlarged entropy effect, endow the ternary OSCs still with ≈70% of initial PCE even after 500 h continuous illumination, whereas only 53% is left in their binary counterparts. These results provide new insight into the molecular design principle for distinctive molecular carbon imides as the third component for efficient and durable PM6:Y6-based OSCs.