Molecular engineering of LRCT-SRCT interplay enables <?A3B2 pi6?>high-performance, high color purity deep-blue OLEDs

The construction of long-range charge-transfer (LRCT) states has emerged as a promising strategy to improve the reverse intersystem crossing (RISC) of multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters, yet balancing LRCT with short-range charge-transfer (SRCT) states remains a significant challenge. To address this, we developed a machine learning-based empirical formula to accurately predict whether LRCT/SRCT-type TADF molecules can retain narrowband emission, thereby aiding the design of novel molecules. Guided by this empirical formula, the proof-of-concept emitter DABNA-TP-DiPXZ exhibited fully hybridized LRCT and SRCT states with deep-blue emission peaking at 445 nm and an impressively narrow full width at half maximum (FWHM) of 19 nm. The corresponding device exhibited outstanding performance, achieving a maximum external quantum efficiency (EQEmax) of 32%, and Commission Internationale de L’Eclairage (CIE) coordinates of (0.14, 0.06). Moreover, it delivered a remarkably high chromaticity efficiency of 367 cd/A, representing the highest value reported among LRCT/SRCT type TADF emitters. These results underscore the remarkable efficiency and color purity of DABNA-TP-DiPXZ, demonstrating the effectiveness of our molecular design strategy in advancing high-performance and high-purity deep-blue emitters.