Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640, P.R. China
State Key Laboratory of polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China
The characteristics of organic light-emitting devices based on tris-(8-hydroxyquinoline) aluminum (Alq3) with NaCl thin films inserted at both anode/organic and organic/cathode interfaces are investigated. We optimize the thicknesses of NaCl at both interfaces, and we get the optimal device with the structure of ITO/NaCl(2.0 nm)/N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1' biphenyl-4,4'-dimaine (NPB)/Alq3/NaCl(2.0 nm)/Al. The device shows much better electroluminescent (EL) performance than that of the as-stated standard device with only LiF buffer layer. The maximal current efficiency and power efficiency is improved by 31% and 67%, the turn-on voltage is also reduced from 4.2 V for the standard device to 3.1 V for our target device. This is due to enhanced electron injection and blocked hole injection, which results in more balanced hole and electron currents.
(Received April 7 2007)
(Revised July 10 2007)
(Accepted July 25 2007)
(Online publication September 21 2007)