Issue 12, 2022

A deep blue thermally activated delayed fluorescence emitter: balance between charge transfer and color purity

Abstract

An efficient blue organic light-emitting diode (OLED) device with high color purity is a challenging issue with technological relevance. Herein, we demonstrated the role of the donor substitution position in a thermally activated delayed fluorescence (TADF) emitter to achieve deep blue emission with improved color purity without reducing the device performance. A novel (4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)(6-(3,6-di-tert-butyl-9H-carbazol-9-yl)pyridin-3-yl)methanone (3BPy-pDTC) was synthesized, where two tert-butyl carbazolyl (DTC) donors linearly connected at the para position of the benzoyl pyridine (3BPy) acceptor core. The 3BPy-pDTC emitter shows a low ΔEST value of 0.19 eV with a subsequent overlap between holes and electrons which leads to a high photoluminescence quantum yield (PLQY) of 93%. Besides, this emitter exhibits narrow emission spectra with a full-width at half maximum (FWHM) of 58 nm. The OLED device using the 3BPy-pDTC dopant provided a high external quantum efficiency (EQE) of 25% with deep blue emission at λmax of 458 nm. 3BPy-pDTC shows color purity in deep blue emission as compared to its meta substituted counterpart (3BPy-mDTC) due to the locked geometry via intramolecular H-bonding and weak excited state charge transfer (CT) interactions. The current study paves the way for developing deep-blue TADF emitters with high efficiency and color purity.

Graphical abstract: A deep blue thermally activated delayed fluorescence emitter: balance between charge transfer and color purity

Supplementary files

Article information

Article type
Paper
Submitted
19 Okt. 2021
Accepted
31 Janv. 2022
First published
31 Janv. 2022

J. Mater. Chem. C, 2022,10, 4886-4893

A deep blue thermally activated delayed fluorescence emitter: balance between charge transfer and color purity

B. Sk, E. Ravindran, U. Deori, N. Yadav, G. P. Nanda and P. Rajamalli, J. Mater. Chem. C, 2022, 10, 4886 DOI: 10.1039/D1TC05027C

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