Actions

Download Analytics Citations

Export to: EndNote  |  Zotero  |  Mendeley

Collections

This file is not currently in any collections.

Thermally Activated Delayed Fluorescence in a Deep Red Dinuclear Iridium(III) Complex: a Hidden Mechanism for Short Luminescence Lifetimes [dataset] Open Access

The high luminescence efficiency of cyclometallated iridium(III) complexes, including those widely used in OLEDs, is typically attributed solely to the formally spin-forbidden phosphorescence process being facilitated by spin-orbit coupling with the Ir(III) centre. In this work, we provide unequivocal evidence that an additional mechanism can also participate, namely a thermally activated delayed fluorescence (TADF) pathway. TADF is well-established in other materials, including in purely organic compounds, but has never been observed in iridium complexes. Our findings may transform the design of iridium(III) complexes by including an additional, faster fluorescent radiative decay pathway. We discover it here in a new dinuclear complex, 1, of the form [Ir(N^C)2]2(u-L), where N^C represents a conventional N^C-cyclometallating ligand, and L is a bis-N^O-chelating bridging ligand derived from 4,6-bis(2-hydroxyphenyl)-pyrimidine. Complex 1 forms selectively as the rac diastereoisomer upon reaction of [Ir(N^C)2(u-Cl)]2 with H2L under mild conditions, with none of the alternative meso isomer being separated. Its structure is confirmed by X-ray diffraction. Complex 1 displays deep-red luminescence in solution or in polystyrene film at room temperature (λem = 643 nm). Variable-temperature emission spectroscopy uncovers the TADF pathway, involving thermally activated re-population of S1 from T1. At room temperature, TADF reduces the photoluminescence lifetime in film by a factor of around 2, to 1 s. The TADF pathway is associated with a small S1–T1 energy gap ΔEST of approximately 50 meV. Calculations that take into account the splitting of the T1 sublevels through spin-orbit coupling perfectly reproduce the experimentally observed temperature-dependence of the lifetime over the range 20 – 300 K. A solution-processed OLED comprising 1 doped into the emitting layer at 5 wt. % displays red electroluminescence, λEL = 625 nm, with an EQE of 5.5% and maximum luminance of 6300 cd m–2.

Descriptions

Resource type

Dataset

Contributors

Creator: Pander, Piotr ¹
Contact person: Pander, Piotr ¹
Zaytsev, Andrey V. ²
Sil, Amit ³
Baryshnikov, Glib V. ⁴
Siddique, Farhan ⁴
Williams, J. A. Gareth ³
Dias, Fernando B. ⁵
Kozhevnikov, Valery N. ²

¹ Faculty of Chemistry, Silesian University of Technology, Poland
² Department of Applied Sciences, Northumbria University, UK
³ Department of Chemistry, Durham University, UK
⁴ Laboratory of Organic Electronics, Department of Science and Technology, Sweden
⁵ Department of Physics, Durham University

Funder

Engineering and Physical Sciences Research Council
Swedish Research Council, Sweden
Olle Engkvist Byggmästare foundation, Sweden
Narodowym Centrum Nauki

Research methods

Other description

Keyword

Iridium complex
Photophysics
OLED
Delayed fluorescence

Subject

Location

Language

Cited in

Identifier

ark:/32150/r2sb397833w
doi:10.15128/r2sb397833w

Rights

Creative Commons Attribution 4.0 International (CC BY)

Publisher

Durham University

Date Created

File Details

Depositor

P.H. Pander

Date Uploaded

23 October 2023, 16:10:36

Date Modified

26 October 2023, 13:10:36

Audit Status

Audits have not yet been run on this file.

Characterization

File format: zip (ZIP Format)

Mime type: application/zip

File size: 397284

Last modified: 2023:10:23 17:36:43+01:00

Filename: Dataset.zip

Original checksum: cbcf68071086b622c97708980e156182