Facile synthesis of multi-resonance ultra-pure-green TADF emitters based on bridged diarylamine derivatives for efficient OLEDs with narrow emission

High color-purity emission with a minimum full width at half maximum (FWHM) is critical for high-resolution displays. Despite the increasing demand for narrow-band emission materials with multi-resonance-induced thermally activated delayed fluorescence (MR-TADF), their development remains challenging from the viewpoint of synthetic chemistry. In this study, we developed a novel one-pot borylation method that does not require the use of hazardous tert-BuLi, and for which the starting materials are not limited to aromatic fluorides and carbazole-based materials. We achieved this by making simple modifications to a boron-nitrogen skeleton. By inserting carbon and oxygen into the skeleton, we created two types of highly efficient green-emitting MR-TADF emitters, namely DMAc-BN and PXZ-BN. This design enabled the suppression of aggregation-induced quenching, which was one of the major challenges faced by MR-TADF emitters developed in the past. OLEDs using our DMAc-BN and PXZ-BN emitters exhibited external quantum efficiencies of 20.3% and 23.3%, respectively, with FWHM values of 49 and 47 nm, respectively. PXZ-BN exhibited pure green emission with CIE coordinates of (0.22, 0.67).