3,6-Diaryl substituted 9-alkylcarbazoles as hole transporting materials for various organic light emitting devices

• Diaryl substituted 9-alkylcarbazoles have been synthesized and tested as materials for hole transporting layers.
• An electroluminescent OLED using one of the materials and Alq3 as emitter demonstrated efficiency of 3.25 cd/A.
• An efficient electro-phosphorescent device with efficiency of 22.5 cd/A was also demonstrated.

Phenyl, naphthyl or biphenyl disubstituted 9-alkylcarbazoles were synthesized by a multi-step synthetic rout. The materials were examined by various techniques including thermogravimetry, differential scanning calorimetry, and electron photoemission spectroscopy. These derivatives were tested as hole transporting materials in OLEDs with Alq3 as the emitter. Some of the devices exhibited promising overall performance with a turn-on voltage of 2.5 V, a maximal current efficiency of 3.25 cd/A and maximum brightness of 8300 cd/m2. The compounds were also applied as hole transporting layers in phosphorescent OLEDs with green phosphorescent emitter of tris(2-phenylpyridine)iridium(III) dispersed in N,N′-dicarbazolyl-4,4′-biphenyl host. An efficient device using 3,6-diphenyl-9-ethylcarbazole as hole transporting layer demonstrated a turn-on voltage of ca. 5 V, a maximum brightness of 9800 cd/m2, and maximum current efficiency of 22.5 cd/A.

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