TB-tPCz is a deep-blue MR-TADF emitter with a rigid structure consisting of an oxygen-bridged boron (DOBNA) core as the electron acceptor and 3,6-diphenylcarbazole attached to the DOBNA core at the para-position to the central boron atom as the electron donor. Though the molecule bears four peripheral bulky tert-butyl groups, interestingly, TB-tPCz still exhibits excellent aggregation induced emission (AIE) in THF/water mixture. The emission intensity of TB-tPCz increases with the ratio of water to the THF the binary solvent. The tert-butyl groups renders TB-tPCz with good solubility in common organic solvents, showing deep blue photoluminescence emission at 422 nm with FWHM of 46 nm.
As a MR-TADF emitter, TB-tPCz shows the small ∆EST, large spin orbit coupling (SOC) constant, and the fast RISC rate. TB-tPCz-based non-doped devices exhibit ultra-deep-blue emissions of 424–428 nm and high color purity owing to their narrow bandwidths of ~ 42 nm, corresponding to the CIE of (x = 0.17, y = 0.06). Optimized TADF device shows a maximum external quantum efficiency (EQEmax) of 15.8%, exhibiting an unprecedented high performance in solution-processed deep-blue TADF-OLEDs.