Researchers add colour to electrochromic glass

The project was carried out by a team from the Fraunhofer Institute for Applied Polymer Research in collaboration with Tilse Formglas.

“Not only can we manufacture panes of glass in a wide range of colours, but we also achieve a much faster switching time than previous models,” said Dr. Volker Eberhardt, a scientist at Fraunhofer IAP.

According to Fraunhofer, manufacturers currently make electrochromic panes with glass that has been coated with a thin film of translucent indium tin oxide or fluorine-doped tin oxide to make the glass electrically conductive.

Two panes are required to make a smart window pane, with one receiving a second, vapour-deposited coating consisting of electrochromic tungsten oxide. The panes are then layered on top of each other with the coatings facing each other and a gel-like electrolyte in between.

When a voltage is applied to the glass, the tungsten oxide coating darkens. When the polarisation is reversed, the pane brightens. In the case of large windows of two to three square meters, it may take up to 15 to 20 minutes before the pane is completely darkened.