3-Aryl substituted 9-alkylcarbazoles as tailored building blocks for hole transporting materials of OLEDs

4-Fluorophenyl, phenyl or naphthyl substituted 9-alkylcarbazoles were synthesized by the multi-step synthetic route. The materials were characterized by elemental analyses, mass and 1H NMR spectroscopy as well as by electron photoemission technique. These derivatives were tested for hole injecting and transporting layers in OLEDs with Alq3 as the emitter. The 3-(1-naphthyl)-9-ethylcarbazole-based OLED exhibited the best performance with a turn-on voltage of ∼3 V, a maximal current efficiency of 0.85 cd/A and maximum brightness of 1270 cd/m2. The device was modified with PEDOT:PSS hole injection layer and demonstrated lower turn-on voltage of ca. 3.0 V, combined with a maximum brightness of 9524 cd/m2 and a maximum photometric efficiency of ca. 5 cd/A.