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.