We survey some recent work related to electrochromic W-oxide-based thin films. The electronic structure of cubic (perovskite) WO₃ and HWO₃ was calculated from first principles. It was found, among other things, that hydroxide formation was energetically favored. Experimental studies were made on films prepared by reactive magnetron sputtering in Ar + O₂ with and without CF₄ addition and substrate bias. Structural studies by atomic force microscopy, x-ray diffraction, infrared reflectance spectroscopy, and Raman spectroscopy indicated that the electron bombardment associated with a positive substrate bias led to grain growth and partial crystallization while maintaining a high density of W equals O double bonds presumably on internal surfaces. Electrochemical and spectrophotometric measurements demonstrated, in particular, that tandem films -- with a thin protective layer of electron bombarded oxide covering a thicker oxyfluoride layer -- were able to combine rapid dynamics of the electrochromism with good durability. Oblique angle sputtering in Ar + O₂ gave films whose microstructure comprised inclined columns, as seen from scanning electron microscopy. Pronounced angular selective transmittance was found to coexist with electrochromism.

Date Published: 23 August 1995
PDF: 13 pages
Proc. SPIE 2531, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIV, (23 August 1995); doi: 10.1117/12.217361

Published in SPIE Proceedings Vol. 2531:
Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIV
Carl M. Lampert; Satyen K. Deb; Claes-Goeran Granqvist, Editor(s)