Energy level alignment at the interface of NPB/HAT-CN/graphene for flexible organic light-emitting diodes

Eonseok Oh, Soohyung Park, Junkyeong Jeong, Seong Jun Kang, Hyunbok Lee, Yeonjin Yi

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Graphene is highly promising as an electrode for flexible optoelectronic devices due to its excellent conductivity and transparency. However, it is necessary to tailor its work function with a charge injection layer in order to obtain favorable energy level alignment for efficient charge injection. An adequate charge injection layer can only be chosen with the understanding of the interfacial electronic structure between a charge transport layer and an electrode. In this study, we investigated the energy level alignment of N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB)/hexaazatriphenylene hexacarbonitrile (HAT-CN)/graphene using in situ ultraviolet and X-ray photoelectron spectroscopy measurements. The effective work function of graphene was significantly increased by 0.94 eV by the HAT-CN hole injection layer (HIL) due to the interface dipole formation. In addition, the charge generation barrier (CGB) between NPB and HAT-CN, which plays a decisive role in charge injection efficiency with a charge generation HIL, was measured to be 0.66 eV. This CGB on graphene is the same as the CGBs on other electrodes, and smaller than that of the widely-used MoO3HIL. Therefore, HAT-CN could be a promising HIL for efficient flexible organic light-emitting diodes with a graphene anode.

Original languageEnglish
Pages (from-to)64-68
Number of pages5
JournalChemical Physics Letters
Volume668
DOIs
Publication statusPublished - 2017 Jan 1

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Organic light emitting diodes (OLED)
Charge injection
Electron energy levels
graphene
light emitting diodes
energy levels
alignment
injection
Electrodes
electrodes
Diamines
Optoelectronic devices
Transparency
Electronic structure
Charge transfer
Anodes
X ray photoelectron spectroscopy
diamines
optoelectronic devices

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Oh, Eonseok ; Park, Soohyung ; Jeong, Junkyeong ; Kang, Seong Jun ; Lee, Hyunbok ; Yi, Yeonjin. / Energy level alignment at the interface of NPB/HAT-CN/graphene for flexible organic light-emitting diodes. In: Chemical Physics Letters. 2017 ; Vol. 668. pp. 64-68.
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Energy level alignment at the interface of NPB/HAT-CN/graphene for flexible organic light-emitting diodes. / Oh, Eonseok; Park, Soohyung; Jeong, Junkyeong; Kang, Seong Jun; Lee, Hyunbok; Yi, Yeonjin.

In: Chemical Physics Letters, Vol. 668, 01.01.2017, p. 64-68.

Research output: Contribution to journalArticle

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