Efficient greenish-blue phosphorescent iridium(III) complexes containing carbene and triazole chromophores for organic light-emitting diodes

•Two Ir(III) complexes with carbene ligands are designed and synthesized.•Both complexes exhibit greenish-blue emission with high efficiency of ∼0.5.•The experimental results are rationalized by the theoretical calculations.•Greenish-blue OLEDs show good efficiencies of 11.78 cd A−1 and 11.43 lm W−1.•A white OLED using one of them as dopant is successfully fabricated.

Two heteroleptic iridium(III) complexes using carbene as cyclometalated ligands and pyridine-triazole as ancillary ligand, namely (fpmi)2Ir(mtzpy) (1) and (fpmi)2Ir(phtzpy) (2) [fpmi = 1-(4-fluorophenyl)-3-methylimdazolin-2-ylidene-C,C2′, mtzpy = 2-(5-methyl-2H-1,2,4-triazol-3-yl)pyridine, phtzpy = 2-(5-phenyl-2H-1,2,4-triazol-3-yl)pyridine], were synthesized and their structural, photophysical and electrochemical properties investigated systematically. Both complexes exhibit bright greenish-blue phosphorescence (λmax ∼490 nm) with quantum yields of about 0.50. Comprehensive density functional theory (DFT) approach was then performed to gain insights into their photophysical and electrochemical characters. The fabrication of organic light-emitting diodes (OLEDs), employing complexes 1 and 2 as phosphorescent dopants, was successfully achieved. Among them, the device based on 1 exhibited considerable power efficiency (ηp) of 11.43 lm W−1 and current efficiency (ηc) of 11.78 cd A−1. With the merit of intrinsic characteristic of complex 1, a white OLED comprised of 1 and one orange phosphor (pbi)2Ir(biq) achieved a peak ηp of 9.95 lm W−1 and ηc of 10.81 cd A−1, together with Commission Internationale de l'Eclairage (CIE) coordinates of (0.34, 0.40). The results indicate that two iridium(III) complexes reported here are promising phosphorescent dyes for OLEDs.

Graphical abstractTwo iridium(III) complexes containing carbene-based cyclometalated ligands and pyridine-triazole ancillary ligand exhibit intense greenish-blue phosphorescent emission. The greenish-blue and white OLEDs using the titled complexes as the dopant emitters show effective electroluminescence efficiencies.Figure optionsDownload full-size imageDownload as PowerPoint slide