Full Paper

Origin of Enhanced Hole Injection in Inverted Organic Devices with Electron Accepting Interlayer

  1. Cephas E. Small3,
  2. Sai-Wing Tsang3,
  3. Junji Kido1,
  4. Shu Kong So2,
  5. Franky So3,*

Article first published online: 24 APR 2012

DOI: 10.1002/adfm.201200185

Issue

Advanced Functional Materials

Advanced Functional Materials

Volume 22, Issue 15, pages 3261–3266, August 7, 2012

Additional Information

How to Cite

Small, C. E., Tsang, S.-W., Kido, J., So, S. K. and So, F. (2012), Origin of Enhanced Hole Injection in Inverted Organic Devices with Electron Accepting Interlayer. Adv. Funct. Mater., 22: 3261–3266. doi: 10.1002/adfm.201200185

Author Information

  1. 1

    Department of Organic Device Engineering, Yamagata University, Yonezawa, Yamagata 992-8510, Japan

  2. 2

    Department of Physics, Hong Kong Baptist University, Kowloon, Hong Kong

  3. 3

    Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 USA

*Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 USA.

Publication History

  1. Issue published online: 1 AUG 2012
  2. Article first published online: 24 APR 2012
  3. Manuscript Revised: 27 JAN 2012
  4. Manuscript Received: 19 JAN 2012

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Keywords:

  • charge injection;
  • inverted;
  • organic electronics

Abstract

Conventional organic light emitting devices have a bottom buffer interlayer placed underneath the hole transporting layer (HTL) to improve hole injection from the indium tin oxide (ITO) electrode. In this work, a substantial enhancement in hole injection efficiency is demonstrated when an electron accepting interlayer is evaporated on top of the HTL in an inverted device along with a top hole injection anode compared with the conventional device with a bottom hole injection anode. Current–voltage and space-charge-limited dark injection (DI-SCLC) measurements were used to characterize the conventional and inverted N,N′-diphenyl-N,N′-bis(1-naphthyl)(1,1′biphenyl)-4,4′diamine (NPB) hole-only devices with either molybdenum trioxide (MoO3) or 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) as the interlayer. Both normal and inverted devices with HAT-CN showed significantly higher injection efficiencies compared to similar devices with MoO3, with the inverted device with HAT-CN as the interlayer showing a hole injection efficiency close to 100%. The results from doping NPB with MoO3 or HAT-CN confirmed that the injection efficiency enhancements in the inverted devices were due to the enhanced charge transfer at the electron acceptor/NPB interface.

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