Triple Long‐Range Charge‐Transfer Channels Enable Efficient LRCT/SRCT Hybridization in Narrowband Deep‐Blue TADF Emission

Abstract

ABSTRACT To accelerate the reverse intersystem crossing (RISC) process of multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters, constructing hybridized long‐range charge‐transfer (LRCT) and short‐range charge‐transfer (SRCT) states within MR‐TADF molecules is a promising strategy. However, the conventional hybrid LRCT‐SRCT strategy proves less effective in enhancing the performance of deep‐blue emitters. In this study, we propose a novel triple‐LRCT‐channel strategy to markedly enhance spin‐orbit coupling (SOC) interactions in deep‐blue LRCT/SRCT type TADF emitters. Based on the pronounced differentiation among the excited states enabled by this strategy, the proof‐of‐concept emitter DABNA‐CN‐PXZ exhibits multiple RISC channels, resulting in a tenfold faster RISC rate than its MR prototype. The corresponding device achieves a high maximum external quantum efficiency of 24.4% and a narrow FWHM of 24 nm, which ranks among the lowest reported for boron‐nitrogen‐based LRCT/SRCT type TADF emitters, arising from the judicious selection of substituents in DABNA‐CN‐PXZ that enables precise control over molecular rigidity and LRCT characteristics. These results demonstrate that DABNA‐CN‐PXZ is among the purest deep‐blue LRCT/SRCT type TADF emitters, delivering excellent device performance under BT.2020‐compliant conditions and thus validating the superiority of our molecular design strategy.