Evaluation of Nitrogen Doping of Tungsten Oxide for Photoelectrochemical Water Splitting

Brian Cole, Bjorn Marsen, Eric Miller, Yanfa Yan, Bobby To, Kim Jones, Mowafak Al-Jassim

Research output: Contribution to journalArticlepeer-review

196 Scopus Citations

Abstract

Thin films of tungsten oxide were fabricated by reactive RF magnetron sputtering for applications related to the direct solar splitting of water. To investigate band gap reduction by nitrogen doping, films were deposited with nitrogen introduced into the sputtering ambient at partial pressures in the range of 0-6 mTorr N2. For dilute doping (pN2 < 2 mTorr), the films exhibit a small increase in band gap, and show a degradation of the carrier collection efficiency. Structurally, X-ray diffraction indicates a decrease in crystallinity with nitrogen incorporation. For higher levels of nitrogen doping (pN2 > 3 mTorr), the diffraction pattern shows the evolution of a new phase that shows an increase in scattering power relative to the pure WO3. For these samples, a reduction of the optical band gap to <2.0 eV is measured. However, the photocurrent density under AM1.5G illumination showed a degradation from 2.68 mA/cm2 for pure WO3 to 0.67 mA/cm2 for the nitrogen doped sample (6 mTorr). The poor photocurrent for the nitrogen doped sample is attributed a degradation of the electron transport properties as a result of a highly defective lattice.

Original languageAmerican English
Pages (from-to)5213-5220
Number of pages8
JournalJournal of Physical Chemistry C
Volume112
Issue number13
DOIs
StatePublished - 2008

NREL Publication Number

  • NREL/JA-520-43396

Keywords

  • conversion efficiencies
  • semiconductor
  • thin films

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