Terpolymer donors incorporating Dichloroquinoxaline segments enable 19.10% efficiency all-polymer solar cells with extremely high open-circuit voltage of 0.986 V

All-polymer solar cells (all-PSCs) possess mechanical flexibility and manufacturing advantages, yet their power conversion efficiency (PCE) still lags behind perovskite solar cells due to high energy loss (E_loss) and trade-off between open-circuit voltage (V_OC) and short-circuit current density (J_SC). This work addresses these limitations by developing terpolymers incorporating 6,7 difluoro-2-((2-hexyldecyl)oxy)-3-methylquinoxaline (Qx) segment (PM6-Qx5, PM6-Qx10, PM6-Qx15) into PM6 main chain. The introduced Qx is expected to lower the HOMO energy level, enhance quinoid resonance and strengthen intermolecular dipole interactions. The results confirm that all terpolymers achieve a lower-lying HOMO energy level, exhibited strong electrostatic potential and demonstrated excellent miscibility with the PY-DT. PM6-Qx10 has achieved the optimal balance between intramolecular and intermolecular interactions compared to PM6, forming a favorable fibrous network morphology for charge generation and transport, while simultaneously reducing non-radiative recombination. The PM6-Qx10:PY-DT device has achieved a high PCE of 19.10 %, with an extremely high V_OC of 0.986 V. Meanwhile, the E_loss is as low as 0.486 eV. Our study not only demonstrates an effective strategy for reducing E_loss in all-PSCs, optimizing active layer morphology, and simultaneously improving V_OC, J_SC and FF, but also provides valuable theoretical guidance for the molecular engineering principles of higher performance all-polymer photovoltaic cells.