Applied Physics A

, Volume 97, Issue 1, pp 1–9 | Cite as

Structural and electronic implications for carrier injection into organic semiconductors

  • Mauro Castellani
  • Ingo Salzmann
  • Philippe Bugnon
  • Shuwen Yu
  • Martin Oehzelt
  • Norbert Koch
Rapid communication

Abstract

We report on the structural and electronic interface formation between ITO (indium-tin-oxide) and prototypical organic small molecular semiconductors, i.e., CuPc (copper phthalocyanine) and α-NPD (N,N′-di(naphtalen-1-yl)-N,N′-diphenyl-benzidine). In particular, the effects of in situ oxygen plasma pretreatment of the ITO surface on interface properties are examined in detail: Organic layer-thickness dependent Kelvin probe measurements revealed a good alignment of the ITO work function and the highest occupied electronic level of the organic material in all samples. In contrast, the electrical properties of hole-only and bipolar organic diodes depend strongly on the treatment of ITO prior to organic deposition. This dependence is more pronounced for diodes made of polycrystalline CuPc than for those of amorphous α-NPD layers. X-ray diffraction and atomic force microscopic (AFM) investigations of CuPc nucleation and growth evidenced a more pronounced texture of the polycrystalline film structure on the ITO substrate that was oxygen plasma treated prior to organic layer deposition. These findings suggest that the anisotropic electrical properties of CuPc crystallites, and their orientation with respect to the substrate, strongly affect the charge carrier injection and transport properties at the anode interface.

PACS

61.05.cp 68.55.J- 72.80.Le 73.30.+y 73.61.-r 

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Mauro Castellani
    • 1
  • Ingo Salzmann
    • 2
  • Philippe Bugnon
    • 3
  • Shuwen Yu
    • 2
  • Martin Oehzelt
    • 4
  • Norbert Koch
    • 2
  1. 1.Institut für Physik und AstronomieUniversität PotsdamPotsdam-GolmGermany
  2. 2.Institut für PhysikHumboldt-Universität zu BerlinBerlinGermany
  3. 3.Institut des MatériauxEcole Polytechnique Fédérale de Lausanne (EPFL)LausanneSwitzerland
  4. 4.Institut für ExperimentalphysikJohannes Kepler Universität LinzLinzAustria

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