Construction of efficient red and near-infrared thermally activated delayed fluorescence molecules via donor engineering strategy: A theoretical perspective

The excited state properties and energy consumption process of donor-acceptor-donor (D-AD) type red and NIR TADF molecules are theoretically studied based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations coupled with the thermal vibration correlation function (TVCF) method. Through investigating the photophysical properties of two reported molecules, the experimental measurements are reasonable explained. Moreover, by employing donor engineering strategy, seven novel TADF molecules are theoretically proposed. Results indicate that small energy gaps and large spin-orbit coupling (SOC) constants between the singlet and triplet excited states are obtained, which are associated with their frontier molecular orbital properties. Consequently, remarkable reverse intersystem crossing (RISC) process and emission process are obtained, efficient red/NIR TADF features are achieved. Our work reveals the relationships between molecular structures and luminescence properties, providing valuable insights to facilitate the development of new efficient red and NIR TADF emitters.