Polymer Acceptor Copolymerized with Luminescent Unit for High‐Performance All‐Polymer Solar Cells with Low Non‐radiative Energy Loss

Reduction of non‐radiative energy loss (Δ E nr ) in all‐polymer solar cells (all‐PSCs) is crucially important for achieving high power conversion efficiencies (PCEs). Herein, an efficient strategy is reported to reduce the Δ E nr by introducing luminescent unit into the backbone of polymer acceptors. Compared to the device based on PM6:PYDT, the Δ E nr in all‐PSC based on PM6:PYDT‐CzP‐9 has decreased from 0.188 to 0.183 eV. This reduction is attributed to the improvement in electroluminescence external quantum efficiency (EQE EL ). The PM6:PYDT‐CzP‐9 device has shown an 18% increase in EQE EL compared to the device based on PM6:PYDT (8.4 × 10 −4 vs 7.1 × 10 −4 ), demonstrating that the incorporation of luminescent unit in polymer acceptors is highly effective in enhancing the electroluminescence performance of all‐PSCs. As a result, the PM6:PYDT‐CzP‐9 device yielded a high V OC of 0.967 V, without the sacrifice of short‐circuit current density (23.42 mA cm −2 ) and fill factor (77.5%), leading to a high PCE of 17.55%.