Noble Dibenzothiophene-Based Bipolar Hosts for Blue Organic Light-Emitting Diodes Using Thermally Activated Delayed Fluorescence

Abstract

Novel thermally activated delayed fluorescence (TADF) host materials for blue electrophosphorescence were designed by combining the electron acceptor dibenzothiophene (DBT) unit and the electron donor acridine derivatives into a single molecular unit by density functional theory (DFT). Depending on the optimal charge transfer, DFT and time-dependent DFT (TD-DFT) calculations for the ground state were performed to obtain the energy of the singlet (S-1) and triplet (T-1) excited states of the TADF material for Hartree-Fock percentage of TD-DFT. The sufficiently large separation between the HOMO and LUMO resulted in a small difference in energy (Delta E-ST) between the S-1 and T-1 states using DFT and TD-DFT calculations. The host molecules retained high triplet energy and showed great potential for use in blue organic light-emitting diodes (OLED). The results showed that these molecules are a good TADF host materials because they have a low barrier to hole and electron injection with a balanced charge transporting property for both holes and electrons, and a small Delta E-ST.