16.3% Efficiency binary all-polymer solar cells enabled by a novel polymer acceptor with an asymmetrical selenophene-fused backbone

Despite the significant progress made recently in all-polymer solar cells (all-PSCs), it is still quite challenging to achieve high open-circuit voltage (V_oc) and short-circuit current density (J_sc) simultaneously in order to further improve their performance. The recent strategy of using selenophene to replace thiophene on the Y6 based polymer acceptors has resulted in significantly improved J_scs of the resulting all-PSCs. However, such modifications have also depressed V_oc, which compromises the overall performance of the devices. Herein, we present the design and synthesis of a novel polymer acceptor, PYT-1S1Se, created by inserting an asymmetrical selenophene-fused framework to precisely manipulate optical absorption and electronic properties. Compared with the selenium-free analog, PYT-2S, and symmetrical selenium-fused analog, PYT-2Se, the PYT-1S1Se derived all-PSCs not only deliver optimized J_sc (24.1 mA cm⁻²) and V_oc (0.926 V) metrics, but also exhibit a relatively low energy loss of 0.502 eV. Consequently, these devices obtain a record-high power conversion efficiency (PCE) of 16.3% in binary all-PSCs. This work demonstrates an effective molecular design strategy for balancing the trade-off between V_oc and J_sc to achieve high-efficiency all-PSCs.