Differences in carbonyl groups and boron acceptors in MR-TADF and full-color emission merging strategies: A theoretical study

Multi-resonant thermally activated delayed fluorescent (MR-TADF) materials, which combine large oscillator strengths, small singlet-triplet energy gaps, high photoluminescence quantum yields, and color purity, have attracted great interest in both experimental and theoretical research in recent years. However, the differences between two classes of MR-TADF, utilizing carbonyl groups and boron atoms as acceptors respectively, have not been clearly delineated, and the implementation of strategies combining both is extremely limited. This limitation hampers the diversity in composition and structure of MR-TADF. In this study, we employed boron as the central acceptor and carbonyl groups as peripheral acceptors, designing and investigating 7 merged systems of MR-TADF molecules. Calculations revealed that, in contrast to the strong acceptor characteristics of boron atoms, carbonyl groups do not exhibit absolute acceptor features, and their resonance effects depend on the surrounding environment. This unique resonance effect induces LRCT features to varying degrees, enabling the emission coverage of these molecules across almost the entire visible spectrum (theoretical emission wavelengths covering 452–751 nm). We gained an understanding of the differences between boron acceptors and carbonyl groups, achieving full-color emission by adjusting only the MR cores. This provides insights into the rational design of complex-component full-color MR-TADF emitters.