A Large Conjugated Rigid Dimer Acceptor Enables 20.19% Efficiency in Organic Solar Cells

Abstract

Non-fullerene acceptors with a large conjugated rigid skeleton are conducive to promoting low disorder and reducing non-radiative recombination loss (ΔEnr), thereby improving open voltage(Voc) 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 (Jsc) 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, which exhibits low energy disorder, small reorganization energy and weakened electro-photon coupling. All of these contribute to a reduction in ΔEnr and improved charge mobility. Benefiting from the above advantages as well as favorable fibrillar morphology, the binary OSC based on PM6:QD-1 showed high and balanced device parameters in Voc , Jsc, and FF, resulting in a high power conversion efficiency (PCE) of 19.46%, which is 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% is achieved, accompanied by all three photovoltaic parameters improved, thanks to the optimized morphology of the active layer. Additionally, a module (13.5cm2) based on the ternary system achieves a high PCE of 17.33%.