Acceptor‐Bridged Engineering Enables Highly Efficient Solution‐Processed Pure‐Green MR‐TADF OLEDs With External Quantum Efficiency of 29% and Small Roll‐Off

The pursuit of next-generation ultrahigh-definition displays has intensified the demand for narrowband emitters with exceptional color purity and high efficiency. Despite the demonstrated superiority of multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters in vacuum-deposited OLEDs, their solution-processing implementation faces significant challenges stemming from inherent molecular rigidity, which compromises solubility, film morphology, and inefficient exciton utilization. Herein, two novel solution-processable, pure-green MR-TADF emitters, DBN-Pym and DBN-PhPym, are reported via an acceptor-bridged engineering strategy that integrates MR cores with electron-withdrawing pyrimidine bridges. Such a design simultaneously enhances the solubility through controlled molecular torsion and precisely modulates the electron distribution via synergistic long- and short-range charge transfer. Consequently, the resulting emitters exhibit narrowband green emission (514/513 nm, full width at half maximum, FWHM: 24-30 nm) with remarkably high photoluminescence quantum yields (PLQYs) of 86% and 99%, respectively. Solution-processed OLEDs exhibit peak emissions at 526/521 nm with Commission Internationale de L'Eclairage (CIE) y coordinates exceeding 0.69. Notably, the DBN-PhPym achieves a record external quantum efficiency (EQE) of 29.0% (maintaining 28.3% at 1000 cd m^-2), with an FWHM of 34 nm, representing state-of-the-art performance for solution-processed MR-TADF devices. This work establishes an effective molecular design strategy for developing efficient narrowband emitters, paving the way for solution-processable ultrahigh-definition displays.