Effects of Hole-Injection Layers on the Performance of Blue Organic Light-Emitting Diodes
GAO Li-yan, ZHAO Su-ling*, XU Zheng, ZHANG Fu-jun, SUN Qin-jun, ZHANG Tian-hui, KONG Chao
Key Laboratory of Luminescence and Optical Information, Ministry of Education，Institute of Optoelectronics Technology, Beijing Jiaotong University, Beijing 100044，China
Abstract：The present work investigates the effects of different buffer layers on the performance of blue organic light-emitting diodes (OLEDs), and compares them with the device with no buffer layer. Two kinds of blue OLEDs with 4,4’-bis(2,2’-diphenyl vinyl)-1,1’-biphenyl (DPVBi) as the emitting layer, N,N’-bis-(1-naphthyl)-N,N’-1-diphenyl-1,1’-biphenyl-4,4’-diamine (NPB) as the hole transporting layer, and copper phthalocyanine (CuPc) and poly(3,4-ethylenedioxythiophene)∶poly(styrenesulphonate) PEDOT∶PSS as the hole injection layer respectively were fabricated with the structures of ITO/CuPc/NPB/DPVBi/BCP/Alq3/Al and ITO/PEDOT∶PSS/NPB/DPVBi/BCP/Alq3/Al. Moreover, the effects of different preparation technology of CuPc on the performance of OLEDs were also investigated. It was found that the performance of the devices with a hole injection layer is better than that of the device without any hole-injection layer. Although the luminance and efficiency of the water-soluble CuPc based device are worse than that of the device with thermally evaporated CuPc, but better than that of the device with water-soluble PEDOT∶PSS. So the water-soluble CuPc is a good hole injection material because it is easier to fabricate the film than traditional CuPc.
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