Improved hole-injection and power efficiency of organic light-emitting diodes using an ultrathin Li-doped ZnO buffer layer

Hsin Hsuan Huang, Sheng Yuan Chu, Po Ching Kao, Yung Chen Chen, Ren Chuan Chang

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

We report on the advantages of an anode buffer layer of Li-doped ZnO (LZO) on the electro-optical properties of organic light-emitting diodes (OLEDs). LZO layers with different thicknesses were prepared by thermally evaporating the LZO powders and then treating them with ultraviolet (UV) ozone exposure. The turn-on voltage of OLEDs decreased from 4 V (4.2 cd m2) to 3 V (5.1 cd m2), the maximum luminance value increased from 16780 to 28150 cd m2 and the power efficiency increased from 2.74 to 5.63 lmW when a 1 nm thick LZO layer was inserted between indium-tin oxide (ITO) anodes and Β - naphthylphenylbiphenyl diamine hole-transporting layers. X-ray and ultraviolet photoelectron spectroscopy were performed to show that the formation of the LZO layer and the work function increased by 0.64 eV when the LZO/ITO layer was treated by UV-ozone for 20 min. The surface of the LZO/ITO film became smoother after the UV-ozone treatment. Thus, the hole-injection energy barrier was lowered by inserting an LZO buffer layer, resulting in the decrease of the turn-on voltage and the increase of the power efficiency in OLEDs.

Original languageEnglish
Pages (from-to)J105-J108
JournalJournal of the Electrochemical Society
Volume154
Issue number3
DOIs
Publication statusPublished - 2007

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry

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