Thermally Activated Delayed Fluorescence Emitter with a Symmetric Acceptor-Donor-Acceptor Structure

Abstract

A thermally activated delayed fluorescence (TADF) emitter with a symmetric acceptordonor-acceptor structure, 3,3'-(9H,9′H-[3,3′-bicarbazole]-9,9′-diyl)bis(9H-xanthen-9-one) (CzX), was developed. Theoretical calculations based on quantum chemistry revealed that the energy difference between the singlet and triplet excited states of CzX was sufficiently small to allow TADF. In addition, the symmetric acceptor-donor-acceptor structure of CzX provided a widely distributed overlap density between its lowest singlet excited state and ground state, which led to a large transition dipole moment between them. These results suggested that CzX is promising as an efficient TADF emitter. An organic light-emitting diode (OLED) containing CzX as an emitting dopant was fabricated by vacuum deposition. The OLED displayed a maximum quantum efficiency of 19.9%. Such a high external quantum efficiency resulted from efficient TADF from CzX.

Thioxanthone-containing blue thermally activated delayed fluorescent emitter

“…When the transition between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) mainly contributes to the electronic con guration of S 1 , a large spatial overlap between the HOMO and LUMO leads to the large rate constant of radiative decay (k r ). 16,17) Besides, according to Fermi's golden rule, a rate constant of RISC (k RISC ) can be expressed as 18) where ΔE ST , k B , and T are the spin-orbit coupling matrix element values (SOCMEVs), the energy gap between S 1 and T 1 , the Boltzmann constant, and temperature, respectively. This equation indicates that large SOCMEVs and small ΔE ST are effective for fast RISC.…”

“…When the transition between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) mainly contributes to the electronic configuration of S 1 , a large spatial overlap between the HOMO and LUMO leads to a large rate constant of radiative decay (k r ). 16,17) Besides, according to Fermi's golden rule, a rate constant of RISC (k RISC ) can be expressed as 18) k…”

Mechanism of high photoluminescence quantum yield of melem

“…Therefore, the basic design of TADF molecules is based on structures with intramolecular donor-acceptor (D-A) moieties or D-A molecule pairs. 19,39 This is because charge transfer (CT) transitions have small exchange integrals between wave functions, yielding a small DE ST . The energy gap, DE ST , between S 1 (n,p*) and T 1 (n,p*) tends to be smaller because the overlap integrals of the wave functions of the n and p* orbitals are smaller.…”

Construction of 3,3'‐Bicarbazoles and Indolocarbazoles by Using Visible Light

“…Bicarbazoles (BiCz) are found to showcase potential application in organic electronics, [1,2] photonics, [3] solar cells, [4] and sensing, [5] because of their advantageous/exemplary characteristics, such as low ionization potentials, excellent glassy nature (Tg), and white, [6] blue, [7] green and red luminescence, [8] etc [9] . Besides, they have been identified as important bioskeletons in several natural products and several carbazole derivatives such as bismahanine [10] show excellent anticancer activity [11] …”