High‐performance Ternary Organic Solar Cells With Spectral Uniform Photocurrent Generation by Enhanced Förster Resonance Energy Transfer Induced Reverse Hole Transfer

Abstract The three‐in‐one strategy has obvious advantages in improving the power conversion efficiency of organic solar cells (OSCs). In this work, ternary OSCs are constructed with D18:BTP‐eC9‐4F as the host active layer and SM16, a non‐fullerene acceptor with 3D terminal groups and high fluorescence quantum yield (PLQY), as the ternary component. The optimal ternary OSCs have a power conversion efficiency (PCE) of 19.28%. The device performance and the excited state dynamics of ternary OSCs with various BTP‐eC9‐4F/SM16 weight ratios are studied. The device performance results show that the high PLQY of SM16 reduces the non‐radiative energy loss and improves the open circuit voltage. The 3D terminal group and high solubility of SM16 are conducive to adjusting the morphology and benefit in forming bi‐continuous interpenetrating networks, thus facilitating the photocurrent generation, and improving the fill factor. Femtosecond transient absorption spectra show that the proper introduction of SM16 can improve the Förster resonance energy transfer rate and thus improve the reverse hole transfer efficiency. This helps improve the charge generation efficiency and achieves a higher PCE. This study highlights the potential of the 3D terminal group acceptors with high PLQY as a ternary component material for improving the PCE of ternary OSCs.