Issue 31, 2022

Deep-red light-emitting electrochemical cells based on phosphor-sensitized thermally activated delayed fluorescence

Abstract

Solid-state light-emitting electrochemical cells (LECs) show the advantages of a simple fabrication process, low-voltage operation, and compatibility with inert electrodes. However, even phosphorescent deep-red LECs still suffer from limited device efficiencies. In this work, we demonstrate efficient deep-red LECs based on phosphor-sensitized thermally activated delayed fluorescence (TADF). A phosphorescent ionic transition metal complex (iTMC) is used as the host and a deep-red TADF emitter is employed as the guest. With rapid intersystem crossing (ISC) to promote intramolecular singlet-to-triplet energy transfer in the iTMC, efficient host–guest Förster energy transfer ensures harvesting both singlet and triplet excitons on the host molecules. In addition, the effective reverse intersystem crossing (RISC) process can further recycle the guest triplet excitons coming from the host–guest Dexter energy transfer and direct triplet exciton formation on the guest under electrical excitation. Therefore, host–guest deep-red LECs doped with a 0.25 wt% guest achieve a peak EQE of up to 5.11%, which is among the highest reported for deep-red LECs. Analysis of the device efficiency by evaluating related device parameters implies that more than 73% of the excitons on the guest molecules can be gathered for electroluminescence (EL). It approaches 3× EL efficiency of fluorescent devices, which can only harvest 25% excitons for light emission, and thus confirms an efficient RISC process to recycle the guest triplet excitons. These results reveal that phosphor-sensitized TADF is useful for achieving highly efficient fluorescent deep-red LECs. However, triplet–triplet annihilation on the guest still hinders the improvement of the device efficiency of the phosphor-sensitized TADF LECs when the guest doping concentration or device current is higher.

Graphical abstract: Deep-red light-emitting electrochemical cells based on phosphor-sensitized thermally activated delayed fluorescence

Supplementary files

Article information

Article type
Paper
Submitted
26 4月 2022
Accepted
11 7月 2022
First published
12 7月 2022

J. Mater. Chem. C, 2022,10, 11211-11219

Deep-red light-emitting electrochemical cells based on phosphor-sensitized thermally activated delayed fluorescence

Y. Chen, Y. Wang, C. Lu and H. Su, J. Mater. Chem. C, 2022, 10, 11211 DOI: 10.1039/D2TC01727J

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements