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Excimer or aggregate? Near infrared electro- and photoluminescence from multimolecular excited states of N^C^N-coordinated platinum(ii) complexes

Pander, Piotr; Sil, Amit; Salthouse, Rebecca J.; Harris, Christopher W.; Walden, Melissa T.; Yufit, Dmitry S.; Williams, J.A. Gareth; Dias, Fernando B.

Excimer or aggregate? Near infrared electro- and photoluminescence from multimolecular excited states of N^C^N-coordinated platinum(ii) complexes Thumbnail


Authors

Amit Sil

Rebecca J. Salthouse

Christopher W. Harris

Melissa T. Walden



Abstract

We present an experimental and theoretical study of aggregate excited states formed by complexes of the type Pt(N^C^N)Cl, which display near-infrared (NIR) photoluminescence in film and NIR electroluminescence in OLED devices. Here, N^C^N represents a tridentate cyclometallating ligand binding through a central benzene ring and two lateral N-heterocycles. A simple theoretical model for the bimolecular excited states of these complexes accounts for the observed behaviour in terms of metal–metal-to-ligand charge-transfer (MMLCT). Detailed photophysical study provides insight into the kinetic properties of Pt–Pt excimers in solution, in films processed from solution, and in vacuum-deposited films. A clear distinction between emission from dimers and higher oligomers (e.g., trimers and tetramers) is evident. We also demonstrate an alternative approach to the architecture of OLEDs based on aggregate states of Pt(II) complexes. An emissive layer (EML) as thin as 1 to 2 nm can be employed, without compromising the efficiency, while reducing the use of the precious-metal compound by >90% compared to typical devices using EMLs of ∼20–40 nm thickness. For example, OLEDs obtained with an EML of 2 nm thickness display an EQE of 1.2% with λEL = 817 nm and a maximum radiosity of 1.46 mW cm−2. As for the photoluminescence of films, the longest-wavelength electroluminescence from devices employing pristine films of emitter is also attributed to trimers and tetramers.

Citation

Pander, P., Sil, A., Salthouse, R. J., Harris, C. W., Walden, M. T., Yufit, D. S., …Dias, F. B. (2022). Excimer or aggregate? Near infrared electro- and photoluminescence from multimolecular excited states of N^C^N-coordinated platinum(ii) complexes. Journal of Materials Chemistry C Materials for optical and electronic devices, 10(40), 15084-15095. https://doi.org/10.1039/d2tc01511k

Journal Article Type Article
Acceptance Date Aug 9, 2022
Online Publication Date Aug 12, 2022
Publication Date Oct 28, 2022
Deposit Date Oct 29, 2022
Publicly Available Date Oct 31, 2022
Journal Journal of Materials Chemistry C
Print ISSN 2050-7526
Electronic ISSN 2050-7534
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 10
Issue 40
Pages 15084-15095
DOI https://doi.org/10.1039/d2tc01511k

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