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

Pander, Piotr Henryk; Zaytsev, Andrey; Sil, Amit; Williams, J.A. Gareth; Lanoë, Pierre-Henri; Kozhevnikov, Valery Nikolaevich; Dias, Fernando B.

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.

Citation

Pander, P. H., Zaytsev, A., Sil, A., Williams, J. G., Lanoë, P.-H., Kozhevnikov, V. N., & Dias, F. 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 Materials for optical and electronic devices, 9(32), 10276-10287. https://doi.org/10.1039/d1tc02562g

• Journal Article Type: Article
• Acceptance Date: Jul 14, 2021
• Online Publication Date: Jul 16, 2021
• Publication Date: Aug 28, 2021
• Deposit Date: Jul 21, 2021
• Publicly Available Date: Jul 22, 2021
• Journal: Journal of Materials Chemistry C Materials for optical and electronic devices
• Print ISSN: 2050-7526
• Electronic ISSN: 2050-7534
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 9
• Issue: 32
• Pages: 10276-10287
• DOI: https://doi.org/10.1039/d1tc02562g
• Public URL: https://durham-repository.worktribe.com/output/1239162