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 (S₁) and the lowest triplet (T₁) 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 S₁ state and the T₁ state (ΔE_ST) value (0.353 eV), which is favorable for a reverse intersystem crossing process from T₁ to S₁ states, and an emission wavelength of 467.4 nm with a sufficiently large oscillator strength (F) value (0.1109).

Keywords:

• Density functional theory (DFT)
• Time-dependent density functional theory (TD-DFT)
• Organic light-emitting diode (OLED)
• Thermally activated delayed fluorescence

Acknowledgment

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2017R1D1A1B03028107) and (No. 2015R1A6A1A03031833).