Abstract: Building blocks and heteroatom alignments are two determining factors in designing multiple resonance (MR)-type thermally activated delayed fluorescence (TADF) emitters. Carbazole-fused MR emitters, represented by CzBN derivatives, and the heteroatom alignments of ν-DABNA are two star series of MR-TADF emitters that show impressive performances from the aspects of building blocks and heteroatom alignments, respectively. Herein, a novel CzBN analog, Π-CzBN, featuring ν-DABNA heteroatom alignment is developed via facile one-shot lithium-free borylation. Π-CzBN exhibits superior photophysical properties with a photoluminescence quantum yield close to 100% and narrowband sky blue emission with a full width at half maximum (FWHM) of 16 nm/85 meV. It also gives efficient TADF properties with a small singlet-triplet energy offset of 40 meV and a fast reverse intersystem crossing rate of 2.9*105 s-1. The optimized OLED using Π-CzBN as the emitter achieves an exceptional external quantum efficiency of 39.3% with a low efficiency roll-off of 20% at 1000 cd m-2 and a narrowband emission at 495 nm with FWHM of 21 nm/106 meV, making it one of the best reported devices based on MR emitters with comprehensive performance.
链接：https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202306413
