Theoretical study of thermally activated delayed fluorescence from benzofuro[2,3-b]pyridine based emitters

Abstract

Novel thermally activated delayed fluorescence (TADF) materials with 6-position modified benzofuro[2,3-b]pyridine (6BFP) as an electron acceptor and phenylcarbazole derivatives [9-phenyl-1,8-diamethyl-9H-carbazole (PmCz), and 9,9',9''-(benzene-1,2,3-triyl)tris(9H-carbazole) (BtCz)] as electron donors were designed, and a theoretical study of their electronic and optical properties was conducted to determine their utility for blue organic light-emitting diodes (OLEDs). Using density functional theory (DFT) and time-dependent DFT calculations, we obtained the electron distribution of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) and the energy of the lowest singlet (S-1) and the lowest triplet (T-1) excited states. We show that BtCz-6BFP would be a suitable sky-blue TADF emitter because it has a sufficiently small energy difference between the S-1 state and the T-1 state (Delta E-ST) value (0.353 eV), which is favorable for a reverse intersystem crossing process from T-1 to S-1 states, and an emission wavelength of 467.4 nm with a sufficiently large oscillator strength (F) value (0.1109).