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PreprintCC BY-NC-NDChemRxiv

Harnessing TADF in iridium(III) complexes for nearly 20% external quantum efficiency in solution-processed OLEDs

  • Paulina H. Marek-Urban1,2,3
  • Hector Miranda-Salinas4
  • Kinga Kępska1,2
  • Marilia Gabriela Belarmino Cabral1,2
  • Karol Erfurt1
  • Karolina Wrochna3
  • Andrew P. Monkman4
  • Piotr Pander1,2
4 affiliations
  1. 1Faculty of Chemistry, Silesian University of Technology, M. Strzody 9, Gliwice, Poland, 44-100
  2. 2Centre for Organic and Nanohybrid Electronics, Silesian University of Technology, Konarskiego 22B, Gliwice, Poland, 44-100
  3. 3Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, Warsaw, Poland, 00-664
  4. 4Department of Physics, Durham University, South Road, Durham, United Kingdom, DH1 3LE
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Abstract

Our work presents three new di-iridium(III) complexes Ir-H, Ir-F, and Ir-CN displaying strong thermally activated delayed fluorescence (TADF) behaviour. These complexes were obtained by variating the group R = H, F, CN at the 5-position on the pyrimidine-based bridging ligand. Our Ir(III) complexes emit green to orange photoluminescence in polystyrene film, with λPL in the range from 529 nm for Ir-H to 583 nm for Ir-CN and with unity photoluminescence quantum yield. They display clear negative solvatochromism in solution, in line with the metal-to-ligand charge-transfer (MLCT) nature of their excited states. Their TADF performance has been established in a temperature-dependent experiment with the ΔE S-T ranging 30-46 meV with the lowest value reported for orange emitter Ir-CN. Our work is complemented with a detailed computational study and modelling. We report the record high solution-processed organic light-emitting diode (OLED) external quantum efficiency (EQE) of 19.5% recorded for emitter Ir-F at luminance of 1000 cd m -2 . This remarkable achievement presents the highest EQE figure for any iridium(III) complex for which TADF has been reported and double the previous record. The low efficiency roll-off of this device is a result of extremely short PL lifetimes τ PL ~300 ns and high radiative decay rate constants k r ~3×10 6 s -1 of the Ir(III) TADF emitters.

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Cite

BibTeXRIS
BibTeX
@misc{marekurban2026harnessing,
  title = {{Harnessing TADF in iridium(III) complexes for nearly 20% external quantum efficiency in solution-processed OLEDs}},
  author = {Paulina H. Marek-Urban and Hector Miranda-Salinas and Kinga Kępska and Marilia Gabriela Belarmino Cabral and Karol Erfurt and Karolina Wrochna and Andrew P. Monkman and Piotr Pander},
  howpublished = {ChemRxiv},
  year = {2026},
  month = sep,
  doi = {10.26434/chemrxiv.15008378/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008378/v1},
  note = {CC BY-NC-ND},
}
RIS
TY  - UNPB
TI  - Harnessing TADF in iridium(III) complexes for nearly 20% external quantum efficiency in solution-processed OLEDs
AU  - Paulina H. Marek-Urban
AU  - Hector Miranda-Salinas
AU  - Kinga Kępska
AU  - Marilia Gabriela Belarmino Cabral
AU  - Karol Erfurt
AU  - Karolina Wrochna
AU  - Andrew P. Monkman
AU  - Piotr Pander
PY  - 2026
DA  - 2026/09/06
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15008378/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008378/v1
AB  - Our work presents three new di-iridium(III) complexes Ir-H, Ir-F, and Ir-CN displaying strong thermally activated delayed fluorescence (TADF) behaviour. These complexes were obtained by variating the group R = H, F, CN at the 5-position on the pyrimidine-based bridging ligand. Our Ir(III) complexes emit green to orange photoluminescence in polystyrene film, with λPL in the range from 529 nm for Ir-H to 583 nm for Ir-CN and with unity photoluminescence quantum yield. They display clear negative solvatochromism in solution, in line with the metal-to-ligand charge-transfer (MLCT) nature of their excited states. Their TADF performance has been established in a temperature-dependent experiment with the ΔE S-T ranging 30-46 meV with the lowest value reported for orange emitter Ir-CN. Our work is complemented with a detailed computational study and modelling. We report the record high solution-processed organic light-emitting diode (OLED) external quantum efficiency (EQE) of 19.5% recorded for emitter Ir-F at luminance of 1000 cd m -2 . This remarkable achievement presents the highest EQE figure for any iridium(III) complex for which TADF has been reported and double the previous record. The low efficiency roll-off of this device is a result of extremely short PL lifetimes τ PL ~300 ns and high radiative decay rate constants k r ~3×10 6 s -1 of the Ir(III) TADF emitters.
ER  -