Band edge disorder producing Urbach's tail and enhanced photochromic efficiency caused by density of states inside band gap in tungsten oxide films

Takaya Kubo, Yoshinori Nishikitani, Nobuyuki Kuroda, Mitsuo Matsuno

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The band gap of WO3 and its disorder at the band edge were evaluated, assuming Urbach's rule, and flat-band potentials (Vfbs) were also measured on WO3 films with high photochromic efficiency (HPE) and low photochromic efficiency (LPE). The main results are as follows: 1) the optical absorption of LPE-WO3 sets on at higher photon energy than that of HPE-WO3, 2) HPE-WO3 has the density of states deeper in the band gap than LPE-WO3 does, and 3) Vfb of HPE-WO3 is higher than that of HPE-WO3. These results indicate that the band edge disorder of WO3, which is closely related to Urbach's tail, determines the Fermi level position, and therefore makes Vfb high; they also imply that a high Vfb, dissociates optically excited electrons and holes to make colors center resulting in photochromism at a high efficiency.

Original languageEnglish
Pages (from-to)5361-5366
Number of pages6
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume35
Issue number10
Publication statusPublished - 1996
Externally publishedYes

Keywords

  • Electrochromism
  • Flat band potential
  • Photochromism
  • Tungsten oxide
  • Urbach's tail

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)
  • Engineering(all)

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