Efficient bipolar host materials based on carbazole and 2-methyl pyridine for use in green phosphorescent organic light-emitting diodes

Abstract

Two host materials based on the carbazole/pyridine end-capping group were designed and synthesized to produce green phosphorescent organic light-emitting diodes. One of the host materials, 9-[9,9-diethyl-2-(6-methylpyridin-2-yl)-9H-fluoren-7-yl]-9H-carbazole (2), exhibited excellent properties for use in efficient green phosphorescent organic light-emitting diodes. A device using compound 2 as the host material with the green phosphorescence dopant bis[2-(1,1′,2′,1′′-terphen-3-yl)pyridinato-C,N]iridium(III)(acetylacetonate) had an external quantum efficiency of 10.7%, a power efficiency of 17.27 lm W⁻¹ and a luminance efficiency of 39.72 cd A⁻¹ at 20 mA cm⁻², with CIE chromaticity coordinates of (0.34, 0.62) at 8.0 V.