Syntheses and characterization of 6,6′-diaryl-9,9′-dialkyl[3,3′]bicarbazoles as materials for electroluminescent devices

• Diaryl-substituted [3,3′]bicarbazoles were synthesized and characterized.
• These derivatives used as hole transporting layers in OLEDs.
• Efficiency of 4.2 cd/A and brightness exceeding 12,200 cd/m2 were obtained.

Electro-active materials containing 6,6′-diaryl-substituted [3,3′]bicarbazole core were synthesized by multistep synthetic rote and characterized. The derivatives were examined by differential scanning calorimetry and demonstrated formation of amorphous materials with rather high glass transition temperatures. The synthesized compounds have been tested as hole transporting layers in simple OLED devices with Alq3 as the emitter/electron transporting layer. The green devices containing hole transporting films of diphenyl-9,9′-diethyl-[3,3′]bicarbazole exhibited the best overall performance (turn-on voltage: 3.5 V, maximum photometric efficiency: 4.2 cd/A, maximum brightness: ∼12,200 cd/m2).