A benzoindole-cored building block for deep blue fluorescent materials: synthesis, photophysical properties, and applications in organic light-emitting diodes

Abstract

Deep blue fluorescent materials are crucial in the commercialization of organic light-emitting diodes (OLEDs) for full-color displays or solid-state lighting sources. In this work, a series of aromatic ring compounds, based on a newly designed 2-(pyridine-4-yl)-3-phenyl-1H-benzo[g]indole core, have been synthesized, on which donor (D) and acceptor (A) groups are bonded in a Ψ-type configuration, forming a D–π–A–π–D structure. The electronic structure and photophysical properties have been explored, as well as the applications in the blue OLEDs. The results show that multistate couplings exist between the three D–π–A–π–D moieties, resulting in a high photoluminescence quantum yield up to 76.01% peaking at around 410 nm, and a depressed efficiency roll-off at high luminance. The deep blue OLEDs based on CzCNBPyIp emitter exhibits stable emission peaking at 416 nm with a negligible efficiency roll-off at a high luminance range of 1 000–10 000 cd m⁻², and corresponding CIE_x,y = (0.162, 0.085) and maximum EQE = 2.6%, making it one of the highest performing solution-processed deep blue fluorescent devices. This work provides an alternative method for the deep blue fluorescent material design toward solution processing OLEDs.