Efficient red phosphorescent OLEDs employing carbazole-based materials as the emitting host

We report on the synthesis and characterization of a new series of electro-active carbazole-based compounds. The derivatives are thermally stable amorphous materials with glass transition temperatures in the range of 54-93 degrees C. Electron photoemission spectra of thin layers of the materials show ionization potential in the range of 5.4-5.5 eV. The carbazole-based derivatives are fully characterized and their spectroscopic properties are determined by absorption and photoluminescence. All developed materials and commonly-used tris(4-carbazoy1-9-ylphenyl)amine (TCTA) were used as hosts in red phosphorescent organic light-emitting diodes (OLEDs) for comparison. Results indicate that a device with 3-[bis(9-ethylcarbazol-3-yl)methyl]-9-hexylcarbazole exhibited superior performance with peak efficiencies of 8.4%, 5.3 cd/A and 5.5 lm/W. (C) 2015 Elsevier Ltd. All rights reserved.