Author/Authors :
Kim، نويسنده , , Ji-Hoon and Seo، نويسنده , , Jaewon and Kwon، نويسنده , , Dae-Gyeon and Hong، نويسنده , , Jong-Am and Hwang، نويسنده , , Joohyun and Choi، نويسنده , , Hong Kyw and Moon، نويسنده , , Jaehyun and Lee، نويسنده , , Jeong-Ik and Jung، نويسنده , , Dae Yool and Choi، نويسنده , , Sung-Yool and Park، نويسنده , , Yongsup، نويسنده ,
Abstract :
The carrier injection efficiencies of organic light-emitting diodes with a multilayer graphene (MLG) anode were compared for different hole injection layers (HIL). The energy level alignments at the hole injecting interface were also studied by using the ultraviolet photoelectron spectroscopy (UPS). We employed 1,1-bis[4-[N,N′-di(p-tolyl)amino]phenyl]cyclohexane (TAPC) as the hole transporting materials, while N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB) or 1,4,5,8,9,12-hexaaza-triphenylene-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) was used as the HIL. The current–voltage characteristics of hole-only devices showed that the MLG anode was only slightly inferior to the indium-tin oxide (ITO) anode in hole injection performance for all the HIL layers. The best efficiency was observed for both MLG and ITO anodes with HAT-CN HIL. We compared UPS-measured energy level alignment of TAPC/HIL/MLG interface for different HILs and concluded that the unique charge generation interface at TAPC/HAT-CN played a crucial role for the improved performance of HAT-CN HIL.
