Issue 18, 2024

Efficient thermally activated delayed fluorophores featuring multi-donor arms and a π-extended acceptor core

Abstract

Thermally activated delayed fluorophores often face challenges related to low solid-state luminescence efficiency and inefficient spin–flip processes, compromising their performances in organic light-emitting diodes. Herein, we introduce two new thermally activated delayed fluorophores, namely 4CzAQ and 4CzDP, based on a π-extended acceptor core (acenaphtho[1,2-b]quinoxaline/dibenzo[a,c]phenazine) and four electron-donating carbazolyl arms. These new emitters feature a propeller-like sterically demanding configuration, which mitigates emission quenching in the solid state. Crucially, this design strategy results in a dense charge-transfer excited-state alignment and strategically introduces locally excited triplet states from the acceptor within the alignment to facilitate spin flipping by a spin–vibronic coupling mechanism. The luminescence properties and spin-flipping efficiency can be finely tuned by varying the acceptor unit, depending on its π-conjugation extension and energy level. A device doped with 10 wt% of the optimal emitter, 4CzAQ, achieves a remarkable electroluminescence performance with an external quantum efficiency of 26.8% and a peak at 555 nm. The combined steric and electronic modulation arising from this molecular design offers a compelling strategy to address critical challenges in thermally activated delayed fluorophores.

Graphical abstract: Efficient thermally activated delayed fluorophores featuring multi-donor arms and a π-extended acceptor core

Supplementary files

Article information

Article type
Paper
Submitted
13 Mar 2024
Accepted
13 Apr 2024
First published
16 Apr 2024

J. Mater. Chem. C, 2024,12, 6406-6414

Efficient thermally activated delayed fluorophores featuring multi-donor arms and a π-extended acceptor core

B. Liu, S. Chen, W. Chen, L. Xing, J. Tan, W. Wu, X. Liu, J. Chen, H. Zhang and Y. Huo, J. Mater. Chem. C, 2024, 12, 6406 DOI: 10.1039/D4TC00988F

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