C‐H Arylation‐Derived Dimeric Molecule Donors for 20.07% Efficiency Ternary Organic Solar Cells

Abstract Dimeric molecule (DM) materials as the third components are proven to improve the device stability and power‐conversion‐efficiency (PCE) simultaneously of organic solar cells (OSCs). However, most DM materials used to construct high‐performance OSCs are synthesized through multistep Stille coupling reactions involving organotin reagents, suffer from a serious environmental problem. Herein, two DM donors (DM‐C6 and DM‐C12) with different alkyl‐linker lengths are firstly developed using eco‐friendly organotin‐free approaches of direct C‐H activation. Two DM donors offer strong crystallinity, high glass‐transition temperature, and cascade‐like energy level alignment with the PM6:Y6 system, which help to optimize morphology, improve thermal stability, and decrease energy loss of OSCs. Consequently, by blending DM‐C6 and DM‐C12 with PM6:Y6, these OSCs achieve higher PCEs of 17.41–17.57% with synchronously improved photovoltaic parameters compared to their monomer donor‐based device (16.91%), while the DM‐C6‐derived OSC offers superior PCE and stability. Moreover, upon introducing DM‐C6 into the D18:L8‐BO and D18:BTP‐eC9 systems to verify the universality, the related ternary OSCs obtain further boosted PCEs of 19.75% and 20.07%, respectively, which are among the highest values for the reported dimeric photovoltaic materials. This work provides a guideline to develop organotin‐free DM donors with an integration of eco‐friendly chemistry, high device efficiency and stability.