Synthesis and characterization of high Tg carbazole-based amorphous hole-transporting materials for organic light-emitting devices

Novel hole-transporting materials based on carbazole dendrimers, namely G1CBC and G2CBC were synthesized and characterized. They are thermally stable with high glass transition temperatures (T-g) up to 245 degrees C and exhibit chemically-stable redox processes. Double-layer green OLEDs using these materials as the hole-transporting layer (HTL) with the device configuration of ITO/HTL/Alq3/LiF:Al emit brightly (lambda(em) 522-534 nm) from the Alq3 layer with a maximum luminance and low turn-on voltage of 15,890 cd/m(2) and 3.0 V. respectively. Their ability as HTLs in terms of device performance is comparable to the common hole-transporter N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-biphenyl)-4,4'-diamine (NPB), however their thermal properties were far greater than both NPB and N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)benzidine (TPD). (C) 2011 Elsevier Ltd. All rights reserved.