Efficient hole injection material for low operating voltage blue fluorescent organic light emitting diodes

•5,10,15-trimethyl-5H-diindolo[3,2-a:3',2'-c] carbazole (TMDI) as efficient hole injection material.•Excellent hole mobility and a good HOMO level of 5.1 eV•8% reduction in the operating voltage of blue fluorescent OLED.•39% power efficiency improvement in the blue fluorescent OLED.

In this paper, we demonstrate a design and synthesis of efficient hole injecting material, 5,10,15-trimethyl-5H-diindolo[3,2-a:3’,2’-c] carbazole (TMDI), for blue fluorescent organic light emitting diodes (OLEDs). Our synthesized TMDI material has good hole mobility of about 8.9 x10− 4 cm2/Vs and compatible highest occupied molecular orbital level of − 5.1 eV, which are important parameters for excellent hole injection layer (HIL) in the OLED applications. The fabricated blue fluorescent OLEDs with TMDI yield about 8% reduction in operating voltage and 39% of improvement in power efficiency as compare to the widely used HIL material 4,4’,4”-tris-(N-(naphthalen-2-yl)-N-phenyl-amino) triphenylamine. Such performance enhancements are mainly attributed to good hole mobility of TMDI.