High‐Performance Orange Narrow Band Electroluminescent Material Based on Central Symmetry‐Arrangement of Two Fused Multiple Resonance Building Blocks

Abstract The high‐performance multiple resonance thermally activated delayed fluorescence (MR‐TADF) materials with narrowband orange emission have considerable promise in automotive, signal indicators, and medical devices, due to their unique luminescent characteristic and potential applications in the organic electronic industry. However, the methodologies for constructing orange‐emitting materials with high color purity are relatively limited. In this contribution, an orange‐emitting MR‐TADF molecule (namely DBNN) is developed by employing a central symmetry‐arrangement of two fused MR‐building blocks to simultaneously realize spectral redshift and narrowband emission. DBNN exhibits intense orange emission with a narrow full width at half maximum (FWHM) of 28 nm (0.10 eV) and a high photoluminescence quantum yield (ΦPL) of 94%. By utilizing a novel exciplex host and a phosphorescent sensitizer to harvest excitons, the optimized DBNN‐based device demonstrates bright orange electroluminescence with a peak at 588 nm, high maximum external quantum efficiency (EQE) of 32.1% and small FWHM of 39 nm (0.14 eV). Additionally, the device achieves ultrahigh brightness exceeding 145 000 cd m−2 and low efficiency roll‐off, maintaining EQEs of 28.3% and 23.3% at luminescence of 1000 and 10 000 cd m−2, respectively.