Synthesis and characterization of a quinoxaline compound containing polyphenylphenyl and strong electron-accepting groups, and its multiple applications in electroluminescent devices

We report a novel electroluminescent material, 6,7-dicyano-2,3-di-[4-(2,3,4,5-tetraphenylphenyl)phenyl]quinoxaline (CPQ), which can be used as a multifunctional material in organic light-emitting diodes (OLEDs), serving as an effective emitting, electron-transporting, and color-tuning layer. OLEDs employing CPQ as both the emissive and electron transporting layer give bright bluish-green light emission and show a high luminous efficiency of 4.7 cd A−1. In addition, multicolor OLEDs based on CPQ and various hole transport materials (HTMs) were fabricated. We successfully achieved an effective color tuning of emission, from bluish-green through yellowish-green and yellow to reddish-orange, in OLEDs by varying HTMs. Our results provide a simple and effective approach to construction of highly efficient and multicolored OLEDs.