Unveiling the photophysical and excited state properties of multi-resonant OLED emitters using combined DFT and CCSD method.

Multi-resonance thermally-activated delayed fluorescence (MR-TADF) is predominantly observed in organoboron heteroatom-embedded molecules, featuring enhanced performance in organic light-emitting diodes (OLEDs) with high color purity, chemical stability, and excellent photoluminescence quantum yields. However, predicting the impact of any chemical change remains a challenge. Computational methods including density functional theory (DFT) still require accurate descriptions of photophysical properties of MR-TADF emitters. To circumvent this drawback, we explored recent investigations on the CzBX (Cz = carbazole, X = O, S, or Se) molecule as a central building block. We constructed a series of MR-TADF molecules by controlling chalcogen atom embedding, employing a combined approach of DFT and coupled-cluster (CCSD) methods. Our predicted results for MR-TADF emitter molecules align with the reported experimental data in the literature. The variation in the positions of chalcogen atoms embedded within the CzBX2X framework imparts unique photophysical properties.