SEALED ELECTROCHROMIC DEVICE

An improved electrochromic device of the type employing: a working electrode, such as a thin essentially transparent layer of indium/tin oxide coated on glass; the working electrode being coated with an electrochromic layer, such as a thin essentially transparent layer of tungsten oxide; the electrochromic layer being coated with an ion conducting layer, such as a thin essentially transparent layer of a perfluorosulfonate polymer; the ion conducting layer being coated with a counter electrode, such as a thin essentially transparent layer of a layer of gold. The improvement is to operate such a device in an environment of a mixture of an inert gas and the vapor of a high dielectric constant material. This can be done in a sealed double pane window by forming such a device on one of the interior surfaces of the window panes and then filling the remaining space between the panes with a mixture of nitrogen and water vapor.