A large conjugated rigid dimer acceptor enables 20.19% efficiency in organic solar cells†

Non-fullerene acceptors with a large conjugated rigid skeleton are conducive to promoting low disorder and reducing non-radiative recombination loss (ΔE_nr), thereby improving open voltage (V_oc) in organic solar cells (OSCs). However, an unfavorable active layer morphology is often formed due to excessive aggregation of these acceptors, which leads to a low short-circuit current density (J_sc) and fill factor (FF), and significantly lower device efficiencies. In this study, we report a dimer acceptor, QD-1, featuring a large conjugated rigid skeleton that exhibits low energy disorder, small reorganization energy, and weakened electro-photon coupling. All of these factors contribute to a reduction in ΔE_nr and improved charge mobility. Benefiting from the above advantages as well as favorable fibrillar morphology, a binary OSC based on PM6:QD-1 showed high and balanced device parameters in V_oc, J_sc, and FF, resulting in a high power conversion efficiency (PCE) of 19.46%, which is the highest reported for binary OSCs utilizing dimer acceptors. Furthermore, by incorporating QD-1 into the PM6:BTP-eC9 system, a remarkable PCE of 20.19% was achieved, accompanied by an improvement in all three photovoltaic parameters, due to the optimized morphology of the active layer. Additionally, a module (13.5 cm²) based on the ternary system achieved a high PCE of 17.33%.