Low-Temperature Ozone Exposure Technique to Modulate the Stoichiometry of WO(x) Nanorods and Optimize the Electrochromic Performance

Feng Lin, Chi Ping Li, Gang Chen, Robert C. Tenent, Colin A. Wolden, Dane T. Gillaspie, Anne C. Dillon, Ryan M. Richards, Chaiwat Engtrakul

Research output: Contribution to journalArticlepeer-review

34 Scopus Citations


A low-temperature ozone exposure technique was employed for the post-treatment of WO x nanorod thin films fabricated from hot-wire chemical vapor deposition (HWCVD) and ultrasonic spray deposition (USD) techniques. The resulting films were characterized with x-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, UVvisNIR spectroscopy and x-ray photoelectron spectroscopy (XPS). The stoichiometry and surface crystallinity of the WO x thin films were subsequently modulated upon ozone exposure and thermal annealing without particle growth. The electrochromic performance was studied in a LiClO 4propylene carbonate electrolyte, and the results suggest that the low-temperature ozone exposure technique is superior to the traditional high-temperature thermal annealing (employed to more fully oxidize the WO x). The optical modulation at 670nm was improved from 35% for the as-deposited film to 57% for the film after ozone exposure at 150°C. The coloration efficiency was improved and the switching speed to the darkened state was significantly accelerated from 18.0s for the as-deposited film to 11.8s for the film after the ozone exposure. The process opens an avenue for low-temperature and cost-effective manufacturing of electrochromic films, especially on flexible polymer substrates.

Original languageAmerican English
Article numberArticle No. 255601
Number of pages8
Issue number25
StatePublished - 29 Jun 2012

NREL Publication Number

  • NREL/JA-5900-53771


  • manufacturing
  • nanorod
  • ozone exposure
  • thin films


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