Precisely Slight Regulation of Emission Maxima and Construction of Highly Efficient Electroluminescent Materials with High Color Purity.

Abstract

Advanced multiple resonance induced thermally activated delayed fluorescence (MR-TADF) emitters have emerged as a privileged motif for applications in organic light-emitting diodes (OLEDs), because they furnish highly tunable bandgap with emission ranges spanning the visible light region, and have the intrinsic properties of outstanding TADF characteristics and high color purity emission. One of the typical construction paradigms of MR-TADF molecule is based on polycyclization of MR parent core and a representative target model molecule BN-TP has been prepared. Herein, based on the unique nitrogen-atom embedding molecular engineering (NEME) strategy, a series of congeners of BN-TP, namely BN-TP-Nx (x = 1, 2, 3, 4), have been customized. The nitrogen-atom anchored at different position of triphenylene hexagonal lattice entails varying degrees of perturbation to the electronic structure. The newly-constructed emitters have demonstrated the precisely slight regulation of emission maxima of MR-TADF emitters to meet the actual industrial demand, and further enormously enriched the MR-TADF molecular reservoir. The BN-TP-N3-based OLED exhibits ultrapure green emission, with peak of 524 nm, full-width at half-maximum (FWHM) of 33 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.71), and maximum external quantum efficiency (EQE) of 37.3%.