An H₂WO_4(aq)-based sol processing route has been developed to allow the ink jet printing of photocatalytically active WO₃ films. The effect of different heat treatment atmospheres and the addition of triethanolamine upon the structure, composition, optical properties and IPCE response of films printed upon conducting glass substrates (ITO) have been studied using x-ray diffraction, Raman microscopy, UV-visible spectroscopy and photocurrent spectroscopy. It has been discovered that heat treatment under a nitrogen atmosphere inhibits formation of a well defined crystal structure but may extend the tail of the IPCE response curve into the visible range as far as 700 nm. Likewise, the presence of triethanolamine in the precursor sol tends to disrupt the WO₃ crystallization process leading to the formation of amorphous material and residual organic material in the heat treated film. However, UV-visible spectroscopy of these films indicates optical absorption similar to that of crystalline WO3 except with increased absorption in the visible region from 350 nm to 600 nm. These observations are supported by ab initio calculations predicting that the incorporation of nitrogen into the monoclinic WO₃ lattice leads to band gap narrowing and the introduction of mid-gap states.

Date Published: 31 August 2006
PDF: 10 pages
Proc. SPIE 6340, Solar Hydrogen and Nanotechnology, 63400L (31 August 2006); doi: 10.1117/12.680601

Published in SPIE Proceedings Vol. 6340:
Solar Hydrogen and Nanotechnology
Lionel Vayssieres, Editor(s)