Bright Green PhOLEDs Using Cyclometalated Diiridium(III) Complexes with Bridging Oxamidato Ligands as Phosphorescent Dopants

M’hamedi, Ahmed; Fox, Mark A.; Batsanov, Andrei S.; Al-Attar, Hameed A.; Monkman, Andrew P.; Bryce, Martin R.

Abstract

In contrast to monoiridium complexes, the study of diiridium complexes as dopants in phosphorescent organic light-emitting devices (PhOLEDs) is largely unexplored. We now describe the syntheses, detailed NMR analyses, X-ray crystal structures and optoelectronic properties of the new cyclometalated diiridium complexes 5 and 6 in which the iridium centres are bridged by oxamidato ligands. These complexes contain diastereomers – the meso form (ΔΛ) and the racemic form consisting of two enantiomers (ΔΔ and ΛΛ) – with anti-oxamidato bridges. The precursor μ-dichloro-bridged complex 4 is very weakly emissive in solution, whereas the oxamidato bridged complexes 5 and 6 are highly emissive (ΦPL 73% and 63%) with short excited state lifetimes of τP 0.84 and 1.16 μs, respectively. Cyclic voltammetry studies demonstrate that the oxamidato bridging ligand plays a role in mediating intramolecular interactions between the iridium centres. Density functional theory (DFT) calculations and time dependent-DFT (TD-DFT) calculations provide further insights into the structural, electronic, and photophysical properties of the complexes in their ground and excited states. Phosphorescent organic light-emitting diodes (PhOLEDs) using complexes 5 and 6 as the emissive dopants in a simple architecture using a solution-processed active layer give bright green electroluminescence with remarkably high luminance (Lmax > 25[thin space (1/6-em)]000 cd m−2) for diiridium complexes.

Citation

M’hamedi, A., Fox, M. A., Batsanov, A. S., Al-Attar, H. A., Monkman, A. P., & Bryce, M. R. (2017). Bright Green PhOLEDs Using Cyclometalated Diiridium(III) Complexes with Bridging Oxamidato Ligands as Phosphorescent Dopants. Journal of Materials Chemistry C Materials for optical and electronic devices, 5(27), 6777-6789. https://doi.org/10.1039/c7tc00628d

• Journal Article Type: Article
• Acceptance Date: Jun 18, 2017
• Online Publication Date: Jun 28, 2017
• Publication Date: Jan 1, 2017
• Deposit Date: Jun 21, 2017
• Publicly Available Date: Jun 28, 2017
• Journal: Journal of Materials Chemistry C Materials for optical and electronic devices
• Print ISSN: 2050-7526
• Electronic ISSN: 2050-7534
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 5
• Issue: 27
• Pages: 6777-6789
• DOI: https://doi.org/10.1039/c7tc00628d
• Public URL: https://durham-repository.worktribe.com/output/1356633