Effect of cyano substitution in TADF molecules on luminescence properties: A theoretical study.

[Display omitted] • The inhibition of the vibration of the molecules in the aggregated state is the main reason for its AIE mechanism. • It was found that the introduction of cyanine into the acceptor part of the molecule would make △ESTsmaller. • The cyano connections between the acceptor and other acceptors can effectively increase the twist angle and promote the reverse inter-system crossing process. Wise design strategies for efficient thermally activated delayed fluorescence (TADF) molecules are highly desirable. In this work, the effect of cyano-substitution effects on the molecular photophysical properties of five TADF molecules was investigated. The energy gap (△E ST), natural transition orbitals (NTOs) properties, the Huang-Rhys factor and reorganization energies, rate constants for the intersystem crossing (k ISC) and reverse intersystem crossing (k RISC) are analyzed based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT) in combination with the thermal vibration correlation function (TVCF) method to measure method. CzTrzBp-CN-4 has the smallest △E ST and larger spin-orbital coupling (SOC) in the film, leading to larger k RISC , suggesting that the cyano connections between the acceptor and other acceptors can effectively increase the twist angle and promote the k RISC , predicting that it may have TADF properties. [ABSTRACT FROM AUTHOR]