Electrostatic Potential Tuning by Low-Volatility Halogenated Additive: Boosting PTQ10-Based Binary OPV to Near 20%...

The commercialization of organic photovoltaics (OPVs) is hampered by the trade-off between high power conversion efficiency (PCE) and processability, particularly in thick-film and large-area fabrication. Herein, three halogenated diphenyl ether additives with similar structures but distinct physical properties, 1-bromo-2-phenoxybenzene (o-BPB), 1-bromo-4-phenoxybenzene (p-BPB), and 4,4'-oxybis (bromobenzene) (BDPE), are selected to regulate the film-forming process of the PTQ10:m-TEH system. Studies reveal that BDPE exhibits the lowest electrostatic potential (ESP), maximum electron delocalization, and highest decomposition temperature, enabling its retention in the drying film. Through dibromo-induced negative ESP and π-π complementarity with m-TEH, BDPE forms directional noncovalent interactions that delay acceptor nucleation, suppress oversize phase separation, and promote ordered molecular stacking. This ESP-driven interaction simultaneously optimizes the vertical phase distribution, enhances crystallinity, reduces energy loss, extends exciton diffusion lifetime, and accelerates charge transport while suppressing recombination. Benefiting from these synergistic effects, the BDPE-based PTQ10: m-TEH device achieves a PCE of 19.80%, delivers a short-circuit current density of 30.49 mA cm^-2 at 500 nm thickness. BDPE also shows universality in various binary systems (20.11% PCE for D18:L8-BO) and good processability in large-area modules. This work provides an efficient strategy for low-cost thick-film OPVs, offering new theoretical and engineering pathways for their up-scale production.