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

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.