Central Core Asymmetric Acceptor Design Enables Over 20% Efficiency in Binary Organic Solar Cells by Suppressing Non-Radiative Energy Loss and Optimizing Nanomorphology

Abstract

Asymmetric acceptors characterized by core asymmetry exhibit great potential for achieving outstanding efficiency, despite the limited number of relevant studies reported to date. In this work, we propose an asymmetric molecular design strategy that combining core asymmetric substitution with halogenation engineering to design and synthesize two acceptors, namely Ph-2F and Ph-2Cl. The two acceptors showed high photoluminescence quantum yield (PLQY) induced by the asymmetric substitution central core, leading to a reduction in non-radiative energy loss. Meanwhile, the two acceptors demonstrate good miscibility and optimized morphology with the donor PM6. Consequently, the binary OSCs based on PM6:Ph-2F and PM6:Ph-2Cl achieved high power conversion efficiencies (PCEs) of 20.33% (certified 19.70%) and 19.13%, respectively. Note that the efficiency of 20.33%, is the highest value in the asymmetric acceptor based binary OSCs so far. Remarkably, an outstanding PCE of 17.16% was obtained in a 13.5 cm2 module, the highest value for the binary OSCs modules to date. Our work highlights the great potential of core-asymmetry molecular design strategy in improving device performance.