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Dinuclear design of a Pt(II) complex affording highly efficient red emission : photophysical properties and application in solution-processible OLEDs.

Shafikov, Marsel Z. and Daniels, Ruth and Pander, Piotr and Dias, Fernando B. and Williams, J. A. Gareth and Kozhevnikov, Valery N. (2019) 'Dinuclear design of a Pt(II) complex affording highly efficient red emission : photophysical properties and application in solution-processible OLEDs.', ACS applied materials & interfaces., 11 (8). pp. 8182-8193.

Abstract

The light-emitting efficiency of luminescent materials is invariably compromised on moving to the red and near-infrared regions of the spectrum due to the transfer of electronic excited-state energy into vibrations. We describe how this undesirable “energy gap law” can be sidestepped for phosphorescent organometallic emitters through the design of a molecular emitter that incorporates two platinum(II) centers. The dinuclear cyclometallated complex of a substituted 4,6-bis(2-thienyl)pyrimidine emits very brightly in the red region of the spectrum (λmax = 610 nm, Φ = 0.85 in deoxygenated CH2Cl2 at 300 K). The lowest-energy absorption band is extraordinarily intense for a cyclometallated metal complex: at λ = 500 nm, ε = 53 800 M–1 cm–1. The very high efficiency of emission achieved can be traced to an unusually high rate constant for the T1 → S0 phosphorescence process, allowing it to compete effectively with nonradiative vibrational decay. The high radiative rate constant correlates with an unusually large zero-field splitting of the triplet state, which is estimated to be 40 cm–1 by means of variable-temperature time-resolved spectroscopy over the range 1.7 < T < 120 K. The compound has been successfully tested as a red phosphor in an organic light-emitting diode prepared by solution processing. The results highlight a potentially attractive way to develop highly efficient red and NIR-emitting devices through the use of multinuclear complexes.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1021/acsami.8b18928
Publisher statement:This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS applied materials & interfaces copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsami.8b18928
Date accepted:28 January 2019
Date deposited:13 February 2019
Date of first online publication:12 February 2019
Date first made open access:12 February 2020

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