Optical and electrical properties of colored and transparent states of polycrystalline electrochromic WO3 thin films prepared by CVD

WO polycrystalline thin films were prepared by annealing, at 500 or 600°C in air, o black tungsten layers produced by chemical vapour deposition (CVD) of W(CO)6 on fused quartz or Sn02-coated pyrex substrates. The optical and electrical properties were investigated when the electrochromic samples were in the coloured and bleached states. A passage from a semiconductor to metallic behaviour appears during the colouration. This transition is discussed using the Hubbard-Mott and free electron scattering models.

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