A quasiplanar TADF emitter employing a dual-locking strategy enables efficient solution-processed deep blue OLEDs

Abstract

Quasiplanar thermally activated delayed fluorescence (TADF) emitters are promising for high-efficiency deep blue organic light-emitting diodes (OLEDs), but they can seldom be used for wet processes. In this work, a novel solution-processed molecule, BOAC-OH, was developed by grafting a B-OH group onto the prototype molecule BOAC. Driven by synergistic O–H⋯O intramolecular hydrogen bonding and B–C σ bonds, BOAC-OH undergoes a conformational change from a highly twisted form of BOAC to a quasiplanar form. As a result, it achieves remarkably blue-shifted emission below 440 nm and promotes the improvement of the radiative transition rate compared to BOAC. The solution-processed OLED device based on BOAC-OH affords a maximum external quantum efficiency of 10.3% with deep blue emission peaking at 444 nm, corresponding to CIE coordinates of (0.15, 0.08), matching well with the National television system committee blue standard. This work showcases the great potential of this dual-locked strategy in developing deep blue TADF emitters for solution-processed OLEDs