Phenylimidazole-based homoleptic iridium(III) compounds for blue phosphorescent organic light-emitting diodes with high efficiency and long lifetime

• Three homoleptic iridium(III) compounds were proposed for blue phosphorescent OLEDs.
• OLEDs with these blue emitters demonstrated highly efficient and stable characteristics.
• The external quantum efficiency (EQE) of OLED devices was as high as 20.1%.
• The device lifetime (LT50) is larger than 300 h at 1000 cd/m2.

In order to obtain triplet emitters with high stability and efficiency, three homoleptic iridium(III) compounds — specifically, Ir(tpim)3 (1), Ir(mtpim)3 (2), and Ir(itpim)3 (3), where tpim = 1-([1,1′:3′,1″-terphenyl]-2′-yl)-2-(4-fluorophenyl)-1H-imidazole, mtpim = 2-(4-fluorophenyl)-1-(5′-methyl-[1,1′:3′,1″-terphenyl]-2′-yl)-1H-imidazole, and itpim = 2-(4-fluorophenyl)-1-(5′-isopropyl-[1,1′:3′,1″-terphenyl]-2′-yl)-1H-imidazole — were prepared by one-pot reaction of the corresponding phenylimidazole ligand with an Ir(I) complex as a starting material. Compounds 1–3 emit bright sky-blue phosphorescence with λmax = 459–463 nm and phosphorescent quantum efficiencies of 0.38–0.50. Multi-layer phosphorescent organic light-emitting diodes using compounds 1–3 as the triplet emitters and mCBP (3,3-di(9H-carbazol-9-yl)biphenyl) as the host have been fabricated. Compound 3 doped in the emissive layer demonstrate external quantum efficiency as high as 20.1% at 1000 cd/m2. In addition, the device based on compound 1 as an emitter shows a stable lifetime greater than 300 h at 1000 cd/m2, which is one of the best results concerning the device lifetime.

High efficiency and long lifetime are achieved in the blue phosphorescent organic light-emitting diodes by developing terphenyl modified phenylimidazole type phosphorescent emitters.Figure optionsDownload as PowerPoint slide