Computational design of benzo [1,2-b:4,5-b′] dithiophene based thermally activated delayed fluorescent materials

Abstract

A series of benzo [1,2-b:4,5-b′]dithiophene based thermally activated delayed fluorescent molecules have been designed and investigated using density functional theory and time-dependent density functional theory. The theoretical calculations showed that the designed 4, 8-positions of benzo [1,2-b:4,5-b′]dithiophene substituted molecules exhibited a mixed states, which comprised a large proportion of charge transfer components and a small part of locally excited components. The calculated emission wavelengths of the investigated molecules may exhibit long wavelength emission characters. For the designed 4, 8-positions substituted molecule with two [1,2,5]thiadiazolo[3,4-c]pyridine-7-carbonitrile electron-accepting units, which exhibited zero singlet-triplet energy gap, the predicted hole and electron mobilities are 3.43 cm2 v−1 s−1 and 0.18 cm2 v−1 s−1, respectively. Our study may provide new ideas for the design of highly efficient thermally activated delayed fluorescent candidates by realizing the full potential of both singlet and triplet excitons.