Porous antimony-doped tin oxide cathodes formed by supercritical CO₂ treatment at low temperature for silver electro-deposition

Porous antimony-doped tin oxide (ATO) cathodes for silver electrodeposition devices are proposed. The porous structure of the cathodes is obtained by applying supercritical CO₂ (SCCO₂) treatment at 60 °C on spin-coated ATO nanoparticles. The morphological, structural, and electrical properties of the ATO cathodes with the SCCO₂ treatment are investigated. The 0.5 μm thick ATO cathode grown on ITO glass substrates is transparent. However, black state of the device is observed when silver molecules are anchored onto the surface of the ATO cathode during reduction. The average transmission contrast ratio of 12 is obtained in visible spectrum at a driving voltage of 1.5 V and a saturation current density of 5.8 mA/cm². In addition, the electrochromic switching time is 4.5 s for a 0.5 × 0.5 cm device with 65 μm cell gap and 0.08 M electrolyte concentration, and its transmission contrast ratio is better than 9.0 at λ = 633 nm.