A Tetrahedral Bisacridine Donor Enables Fast Radiative Decay in Thermally Activated Delayed Fluorescence Emitter

Abstract

Achieving high efficiency and low efficiency roll-off simultaneously is of great significance for further application of thermally activated delayed fluorescent (TADF) emitters. A balance between radiative decay and reversed intersystem crossing must be carefully established. Herein, we propose a qunolino-acridine (QAc) donor composing two acridine with both planar (pAc) and bended (bAc) geometries. Combining with triazine, a TADF emitter QAc-TRZ is assembled. The pAc provides a well interaction with triazine which ensures a decent TADF behavior, while the bAc offers a delocalization of highest occupied molecular orbital (HOMO) which guarantees an enhancement of radiative decay. Remarkably, QAc-TRZ enables a highly efficient organic light emitting diode (OLED) with maximum external quantum efficiency (EQE) of 37.3 %. More importantly, the efficiencies under 100/1000 cd m À 2 stay 36.3 % and 31.7 %, respectively, and remain 21.5 % even under 10 000 cd m À 2 .

Boosting Luminescence Efficiency of Near-Infrared-II Aggregation-Induced Emission Luminogens via a Mash-Up Strategy of π-Extension and Deuteration for Dual-Model Image-Guided Surgery

“…However, if the aromatic fragment is rationally extended to enhance the intermolecular interactions, the excited state molecular motion theoretically could be restricted to suppress the nonradiative decay. On the other hand, it has been evidenced that π-expansion could enhance f of organic luminogens since the delocalization of HOMO orbitals is improved. − Furthermore, the replacement of high-frequency carbon–hydrogen (C–H) by heavier carbon-deuterium (C–D) can reduce the nonradiative decay caused by high-frequency oscillation. , Besides, the large atomic volume of deuterium also increases the intramolecular steric hindrance of the benzene rings, further suppressing the excited-state intramolecular motion. Therefore, the combination of π-extension and deuteration is expected to develop high-luminescence efficiency NIR-II AIEgens with both faster k r and suppressed k nr , which has not been explored yet.…”

Deuterium Renders Fast Risc and Low Non‐Radiation Decays of TADF Emitters

“…Thermally activated delayed fluorescence (TADF) materials, as the third generation of luminescent materials after phosphorescent materials, have attracted extensive attention from academia and industry due to their theoretically 100% exciton utilization DOI: 10.1002/adom.202300981 efficiency. [1][2][3][4][5][6][7] When the energy gap (ΔE ST ) between the lowest excited singlet state (S 1 ) and the lowest triplet state (T 1 ) of the emitter is less than 0.3 eV, triplet excitons are efficiently upconverted from T 1 to S 1 by a reverse intersystem crossing (RISC) process, and then transitions to the ground state (S 0 ) to achieve delayed fluorescence. [8][9][10][11] Therefore, reducing the energy loss caused by the non-radiative decays of S 1 and accelerating the RISC of T 1 -S 1 are important factors to improve device performance.…”

“…[12][13][14][15][16] The effective strategies to solve this problem are as follows: 1) Introducing large steric hindrance groups such as tert-butyl into the emitters. [17,18] 2) Preparation of more rigid fused ring [6,[19][20] or spiro [21,22] compounds. 3) Introducing intermolecular interactions such as hydrogen bonds.…”

Achieving the Reverse Intersystem Crossing in Chalcone Based Donor‐Acceptor System through Down‐Conversion of Triplet Exciton

“…ii) manipulating the angle between the donor and acceptor in charge transfer molecules [11] . iii) increasing the rigidity and steric hindrance in the D‐A system etc [14–16] …”