Mechanism of hole accumulation at α-NPD/Alq3 interface studied by displacement current measurement

Naoki Sato, Yutaka Noguchi, Yuya Tanaka, Yasuo Nakayama, Hisao Ishii

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

9 Citations (Scopus)

Abstract

We examined the driving mechanism of indium-tin oxide (ITO)/4,4-bis[N-(1- naphthyl)-N-phenyl-amino]biphenyl (α-NPD)/Tris-(8-hydroxiquinolate) aluminum (Alq3)/cathode type organic light-emitting diode (OLED) by using a displacement current measurement (DCM). The DCM enables us to directly calculate the amount of accumulated charge. There exists a maximum value in the amounts of the blocked holes at α-NPD/Alq3 interface. The maximum value was about 120 nC/cm2, this value is consistent with the density of the fixed interfacial charge proposed by Brütting et al. By using hole-only device with Au cathode, we also investigated the hole blocking and the subsequent overflow of hole current beyond the interface. The observed feature can be explained by the hole blocking due to the interfacial charge rather than by that due to the HOMO mismatch at the interface.

Original languageEnglish
Title of host publicationOrganic Light Emitting Materials and Devices XII
DOIs
Publication statusPublished - 2008
EventOrganic Light Emitting Materials and Devices XII - San Diego, CA, United States
Duration: 10 Aug 200812 Aug 2008

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume7051
ISSN (Print)0277-786X

Conference

ConferenceOrganic Light Emitting Materials and Devices XII
Country/TerritoryUnited States
CitySan Diego, CA
Period10/08/0812/08/08

Keywords

  • Accumulation
  • Alq
  • Blocking
  • Displacement current measurement
  • Interfacial charge
  • α-NPD

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