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The Role of Dinuclearity in Promoting Thermally Activated Delayed Fluorescence (TADF) in Cyclometallated, N^C^N-coordinated Platinum(II) Complexes

Pander, Piotr Henryk and Zaytsev, Andrey and Sil, Amit and Williams, J. A. Gareth and Lanoë, Pierre-Henri and Kozhevnikov, Valery Nikolaevich and Dias, Fernando B. (2021) 'The Role of Dinuclearity in Promoting Thermally Activated Delayed Fluorescence (TADF) in Cyclometallated, N^C^N-coordinated Platinum(II) Complexes.', Journal of materials chemistry C., 9 (32). pp. 10276-10287.

Abstract

In this work we present synthesis and an in-depth photophysical analysis of a di-Pt(II) complex with a ditopic bis-N^C^N ligand. The complex exhibits a dual luminescent behaviour by emitting simultaneously delayed fluorescence and phosphorescence. By comparing with the mono-Pt(II) analogue, we demonstrate that thermally activated delayed fluorescence (TADF) is turned on in the di-Pt(II) complex due to the occurrence of three main factors which are not verified in the mono-Pt(II) analogue: a larger singlet radiative rate (krS), a smaller singlet-triplet energy gap (ΔEST) and a longer phosphorescence decay lifetime (τPH). We observe similar trends among other di-Pt(II) complexes and concluded that bimetallic structures promote conditions favourable for TADF to occur. The diplatinum(II) complex also shows a long wavelength-emissive excimer which yields near infrared electroluminescence, λel = 805 nm, in a solution-processed OLED device with EQEmax = 0.51 %. We believe this is the highest efficiency reported to date for an excimer Pt(II) emitter with λel > 800 nm in a solution-processed OLED device.

Item Type:Article
Full text:(AM) Accepted Manuscript
Available under License - Creative Commons Attribution 3.0.
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1039/D1TC02562G
Publisher statement:This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Date accepted:14 July 2021
Date deposited:22 July 2021
Date of first online publication:16 July 2021
Date first made open access:22 July 2021

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