WO3-based electrochromic system with hybrid organic–inorganic gel electrolytes

Thin metal oxide films for a WO3-based symmetric electrochromic system with a nickel oxide layer as the counter electrode have been prepared by spray pyrolysis on SnO2:F coated soda-lime float glass, at a temperature of 670–720 °C and using metal acetylacetonates as precursors. The films have been characterized for composition and morphology by scanning electron microscopy equipped with an X-ray energy dispersive analyzer (SEM/EDAX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Electrochromic properties have been examined in the electrochemical cells of a smart window arrangement using lithium ion doped sol–gel derived organic–inorganic hybrid materials as electrolytes. Hybrids with room-temperature ionic conductivities of 10−4–10−3 Ω−1 cm−1 have been synthesized from tetraethyl orthosilicate (TEOS) with an addition of 35 mass % of organic compounds. Coloration-bleaching of WO3 films with lithium ions from hybrid electrolytes has resulted in the desired modulating the properties in the visible and near infrared spectrum range. An XPS analysis has shown the presence of a lower oxidized tungsten oxide phase (WO2.92) in the WO3 film.