A highly fluorescent pyridine-ended Y6 derivative as a third component for organic solar cells

Abstract

The efficiency of organic solar cells (OSCs) is usually limited by large voltage losses (V_loss), particularly the V_loss associated with the nonradiative recombination (V^non-Rad_oc). Improving the photoluminescence quantum yield (PLQY) and the electroluminescence quantum efficiency (EQE_EL) of the active-layer film has been demonstrated to be crucial to reducing the V^non-Rad_oc. In this study, we report a highly fluorescent molecule (BTP-N) as a third component to increase the EQE_EL and thus improve the V_oc of ternary OSCs. BTP-N, a derivative of Y6, features a pyridine-based end-capping group and exhibits strong fluorescence. When incorporated into the PM6:Y6 binary system with an appropriate ratio, the ternary OSCs achieve a high power conversion efficiency of 17.5% with an improved V_oc of 0.866 V (vs. 0.845 V for binary OSCs). This work indicates that introducing pyridine units is an effective method to increase the fluorescence of the third-component molecule for reducing V^non-Rad_oc and achieving a higher efficiency for OSCs.