Effect of NaCl buffer layer on the performance of organic light-emitting devices (OLEDs)

¹ Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640, P.R. China
² State Key Laboratory of polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China

Corresponding author: shisw@scut.edu.cn

Received: 7 April 2007
Revised: 10 July 2007
Accepted: 25 July 2007
Published online: 21 September 2007

Abstract

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.