Boosting the Efficiency of Layer‐by‐Layer Organic Photovoltaic to Over 19% via TADF‐Mediated Exciton Utilization and Dissociation

ABSTRACT The layer‐by‐layer (LbL) fabrication strategy offers precise control over active layer morphology for organic photovoltaics (OPVs), yet its potential is limited by insufficient utilization of excitons and D:A interfaces near the electrodes. Herein, we incorporate a thermally activated delayed fluorescence (TADF) material, DMAC‐DPS, into LbL‐structured OPVs based on the PM6/L8‐BO system to address these issues. DMAC‐DPS features a donor‐acceptor molecular structure with efficient reverse intersystem crossing (RISC) and energy levels compatible with PM6 and L8‐BO, enabling Förster resonance energy transfer (FRET) and favorable charge transfer. Systematic characterizations were performed to investigate the effect of DMAC‐DPS doping in either donor‐PM6 or acceptor‐L8‐BO layer, as well as in both layers. The optimal performance is achieved by doping 0.1 wt.% DMAC‐DPS into acceptor‐L8‐BO layer, yielding a significantly enhanced PCE of 19.20% from 17.56%, accompanied by a notable increase in J _sc from 25.36 to 27.37 mA/cm ² , while maintaining V _oc of 0.906 V and FF of 77.4%. Mechanistic studies reveal that DMAC‐DPS enhances exciton generation, utilization, and dissociation near electrodes via efficient FRET, and prolongs exciton lifetime through its intrinsic RISC, thereby suppressing recombination and improving charge dynamics. This work establishes a TADF‐mediated strategy to synergistically optimize exciton utilization and charge transport in high‐efficiency LbL OPVs.