The effects of ultra-thin cerium fluoride film as the anode buffer layer on the electrical characteristics of organic light emitting diodes

Hsin Wei Lu, Cheng Che Tsai, Cheng Shong Hong, Po Ching Kao, Yung Der Juang, Sheng Yuan Chu

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing a CeF 3 film as an ultra-thin buffer layer between the indium tin oxide (ITO) electrode and α-naphthylphenylbiphenyldiamine (NPB) hole transport layer, with the structure configuration ITO/CeF 3 (0.5, 1, and 1.5 nm)/α-naphthylphenylbiphenyl diamine (NPB) (40 nm)/tris(8-hydroxyquinoline) aluminum (Alq 3 ) (60 nm)/lithium fluoride (LiF) (1 nm)/Al (150 nm). The enhancement mechanism was systematically investigated via several approaches. The X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy results revealed the formation of the UV-ozone treated CeF 3 film. The work function increased from 4.8 eV (standard ITO electrode) to 5.22 eV (0.5-nm-thick UV-ozone treated CeF 3 film deposited on the ITO electrode). The surface roughness of the UV-ozone treated CeF 3 film was smoother than that of the standard ITO electrode. Further, the UV-ozone treated CeF 3 film increased both the surface energy and polarity, as determined from contact angle measurements. In addition, admittance spectroscopy measurements showed an increased capacitance and conductance of the OLEDs. Accordingly, the turn-on voltage decreased from 4.2 V to 3.6 V at 1 mA/cm 2 , the luminance increased from 7588 cd/m 2 to 24760 cd/m 2 , and the current efficiency increased from 3.2 cd/A to 3.8 cd/A when the 0.5-nm-thick UV-ozone treated CeF 3 film was inserted into the OLEDs.

Original languageEnglish
Pages (from-to)139-144
Number of pages6
JournalApplied Surface Science
Volume385
DOIs
Publication statusPublished - 2016 Nov 1

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Condensed Matter Physics
  • Physics and Astronomy(all)
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

Fingerprint Dive into the research topics of 'The effects of ultra-thin cerium fluoride film as the anode buffer layer on the electrical characteristics of organic light emitting diodes'. Together they form a unique fingerprint.

  • Cite this