Sputtered nickel oxide thin film for efficient hole transport layer in polymer-fullerene bulk-heterojunction organic solar cell

N. Edwin Widjonarko, Erin L. Ratcliff, Craig L. Perkins, Ajaya K. Sigdel, Andriy Zakutayev, Paul F. Ndione, Dane T. Gillaspie, David S. Ginley, Dana C. Olson, Joseph J. Berry

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Bulk-heterojunction (BHJ) organic photovoltaics (OPV) are very promising thin film renewable energy conversion technologies due to low production cost by high-throughput roll-to-roll manufacturing, an expansive list of compatible materials, and flexible device fabrication. An important aspect of OPV device efficiency is good contact engineering. The use of oxide thin films for this application offers increased design flexibility and improved chemical stability. Here we present our investigation of radio frequency magnetron sputtered nickel oxide (NiO x) deposited from oxide targets as an efficient, easily scalable hole transport layer (HTL) with variable work-function, ranging from 4.8 to 5.8 eV. Differences in HTL work-function were not found to result in statistically significant changes in open circuit voltage (V oc) for poly(3-hexylthiophene):[6,6]-phenyl-C 61-butyric acid methyl ester (P3HT:PCBM) BHJ device. Ultraviolet photoemission spectroscopy (UPS) characterization of the NiO x film and its interface with the polymer shows Fermi level alignment of the polymer with the NiO x film. UPS of the blend also demonstrates Fermi level alignment of the organic active layer with the HTL, consistent with the lack of correlation between V oc and HTL work-function. Instead, trends in j sc, V oc, and thus overall device performance are related to the surface treatment of the HTL prior to active layer deposition through changes in active layer thickness.

Original languageEnglish (US)
Pages (from-to)3813-3818
Number of pages6
JournalThin Solid Films
Issue number10
StatePublished - Mar 1 2012


  • Hole transport layer
  • Nickel oxide
  • Organic solar cells
  • Organic-oxide interface
  • Selective interlayer
  • Work-function

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry


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