Oligocarbazole modified hybridized local and charge transfer emitters for efficient solution-processed deep blue organic light-emitting diodes

Herein, two new blue solution-processable hybridized local and charge transfer (HLCT) fluorophores (pCTPI and mCTPI) were designed and synthesized by incorporating oligocarbazole fragment into the HLCT luminogenic triphenylamine-phenanthroimidazole (TPI) molecule. Their HLCT and photoluminescence properties were experimentally and theoretically probed by the solvation effect and density functional theory calculations. These materials exhibited an intense blue emission (440 nm) with a good solution-processed film-forming quality and decent hole mobility (3.98-4.55 x 10-6 cm2 V- 1s- 1), resulting in a successful utilization as non-doped emissive layers in simple solution-processed organic light-emitting diodes (OLEDs). The devices showed deep blue emission (430 nm) with excellent electroluminescence (EL) performance and narrow EL emission as compared to the TPI-based device. Notably, pCTPI-based solution-processed OLED achieved a luminance of 4938 cd m-2 and an external quantum efficiency of 6.35 %.