High-Efficiency and Narrowband OLEDs from Blue to Yellow with Ternary Boron/Nitrogen-Based Polycyclic Heteroaromatic Emitters

The development of boron/nitrogen-based polycyclic heteroaromatic emitters with multiple-resonance thermally activated delayed fluorescence (MR-TADF) property can efficiently promote the advancement of high-efficiency organic light-emitting diodes (OLEDs) with narrowband emission. Herein, a simple strategy to achieve four ternary boron/nitrogen-based polycyclic heteroaromatic emitters (SBON, SBSN, DBON, and DBSN) from pure blue (463 nm) to yellow (553 nm) via tuning the coordination between B/N and heteroatom (O or S) is demonstrated, aiming to increase charge transfer delocalization of the polycyclic heteroaromatic emitters and adjust photo-physical properties. This strategy endows the four emitters with full width at half maximum (FWHM) of 24, 27, 20, and 28 nm, respectively. Additionally, double-boron type green and yellow narrowband emitters (DBON and DBSN) possess 98% photoluminescence efficiencies in doped films. Besides, considerable rate constants of reverse intersystem crossing (RISC) are achieved because of the small singlet-triplet excited state energy gap and large spin-orbit coupling values. Consequently, the OLEDs covering from blue to yellow based on these emitters show the maximum external quantum efficiency of 13.7%, 17.6%, 26.7%, and 21.8%, respectively, with low-efficiency roll-off. These results provide a feasible design strategy to construct boron/nitrogen-based polycyclic heteroaromatic MR-TADF emitters for efficient OLEDs with color-tuning electroluminescence.

Automated summary

This study demonstrates a simple strategy to achieve boron/nitrogen-based polycyclic heteroaromatic emitters with narrowband emission by tuning the coordination between B/N and heteroatom (O or S), resulting in improved photo-physical properties. These emitters show high external quantum efficiency in OLEDs and exhibit low-efficiency roll-off.