Carbazole-carboline core as a backbone structure of high triplet energy host materials

•Carbazole-carboline core as a backbone structure of blue triplet host material.•High quantum efficiency above 20% in blue phosphorescent organic light-emitting diodes.•Management of charge transport properties of host material by controlling the substituent.

A carbazole-carboline core was developed as a backbone structure of high triplet energy host materials and three derivatives of the carbazole-carboline core were synthesized. The carbazole and carboline units were linked via the 3-position of the carbazole and the 6-position of the carboline, and the carbazole-carboline core was modified with cyanophenyl, phenyl and 9-carbazolylphenyl moieties to control the charge transport properties of the host materials. Triplet energy of the carbazole-carboline core derived host materials were above 2.85 eV irrespective of the substituent of the carbazole-carboline core. The new materials were tested as the host materials for blue phosphorescent organic light-emitting diodes and the quantum efficiency of the blue devices reached 23.4%.

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