Dinuclear Design of a Pt(II) Complex Affording Highly Efficient Red Emission: Photophysical Properties and Application in Solution-Processible OLEDs

Shafikov, Marsel Z.; Daniels, Ruth; Pander, Piotr; Dias, Fernando B.; Williams, J.A. Gareth; Kozhevnikov, Valery N.

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.

Citation

Shafikov, M. Z., Daniels, R., Pander, P., Dias, F. B., Williams, J. G., & Kozhevnikov, V. 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 and Interfaces, 11(8), 8182-8193. https://doi.org/10.1021/acsami.8b18928

• Journal Article Type: Article
• Acceptance Date: Jan 28, 2019
• Online Publication Date: Feb 12, 2019
• Publication Date: Feb 27, 2019
• Deposit Date: Feb 13, 2019
• Publicly Available Date: Feb 12, 2020
• Journal: ACS Applied Materials and Interfaces
• Print ISSN: 1944-8244
• Electronic ISSN: 1944-8252
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 11
• Issue: 8
• Pages: 8182-8193
• DOI: https://doi.org/10.1021/acsami.8b18928
• Public URL: https://durham-repository.worktribe.com/output/1308177