Bright green PhOLEDs using cyclometalated diiridium(iii) complexes with bridging oxamidato ligands as phosphorescent dopants. Issue 27 (28th June 2017)

• Record Type: Journal Article
• Authors: M'hamedi, Ahmed; Fox, Mark A.; Batsanov, Andrei S.; Al-Attar, Hameed A.; Monkman, Andrew P.; Bryce, Martin R.
• Is Part Of: Journal of materials chemistry. Volume 5:Issue 27(2017)
• Page Start: 6777
• Page End: 6789
• Publication Date: 2017-06-28
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c7tc00628d
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : In contrast to monoiridium complexes, the study of diiridium complexes as dopants in phosphorescent organic light-emitting devices (PhOLEDs) is largely unexplored. 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 complexes5 and6 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 complex4 is very weakly emissive in solution, whereas the oxamidato bridged complexes5 and6 are highly emissive ( Φ PL 73% and 63%) with short excited state lifetimes of τ P 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 complexes5 and6 as the emissive dopants in a simple architecture using a solution-processed active layer give bright green electroluminescence with remarkably high luminance ( L max > 25 000 cd m −2 ) for diiridium complexes.