Dimer Acceptor Adopting a Flexible Linker for Efficient and Durable Organic Solar Cells

Organic solar cells (OSCs) have advanced rapidly due to the development of new photovoltaic materials. However, the long‐term stability of OSCs still poses a severe challenge for their commercial deployment. To address this issue, a dimer acceptor (dT9TBO) with flexible linker is developed for incorporation into small‐molecule acceptors to form molecular alloy with enhanced intermolecular packing and suppressed molecular diffusion to stabilize active layer morphology. Consequently, the PM6 : Y6 : dT9TBO‐based device displays an improved power conversion efficiency (PCE) of 18.41 % with excellent thermal stability and negligible decay after being aged at 65 °C for 1800 h. Moreover, the PM6 : Y6 : dT9TBO‐based flexible OSC also exhibits excellent mechanical durability, maintaining 95 % of its initial PCE after being bended repetitively for 1500 cycles. This work provides a simple and effective way to fine‐tune the molecular packing with stabilized morphology to overcome the trade‐off between OSC efficiency and stability. A dimer acceptor with flexible linker was designed and synthesized, which not only acts as the third component to enhance the intermolecular packing, but also stabilize the morphology by suppressing the molecular diffusion. As a result, the PM6 : Y6 : dT9TBO based organic solar cells exhibited a high power conversion efficiency of 18.41 % with excellent thermal/photo stability and mechanical performance.