High-Efficiency Narrowband Multi-Resonance TADF Emitters via the Introduction of Bulky Adamantane Unit

The fluorescence quenching of multiple resonance thermally activated delayed fluorescence (MR-TADF) materials has remained a formidable challenge due to the strong π-π packing and intense intermolecular aggregation. To this end, we have designed MR-TADF molecules modified with adamantane with large spatial hindrance, named BN-Ad, to mitigate the intermolecular π-π stacking be-tween the rigid planar skeletons and prevent aggregation-caused quenching. Photoelectric properties of BN-Ad in solutions and thin films were systematically investigated, and the electroluminescence properties were characterized by fabricating organic light-emitting diode devices (OLEDs). The optimized device employing BN-Ad exhibited a maximum external quantum efficiency (EQEmax) of 32.3% peaking at 500 nm with a small full-width at half-maximum (FWHM) of only 35 nm. When the doping ratio in-creased to 50 wt%, the EQEmax can still be maintained at 11.2% with a slightly red-shifted emission peak at 508 nm and moderately widened FWHM of 53 nm.