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

Novel thermally activated delayed fluorescence (TADF) host materials for blue electrophosphores-cence 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 (S1) and triplet (T1) 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 (ΔEST) between the S1 and T1 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 ΔEST.