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Saturday, January 16, 2010

No Curtains Needed: Soladigm, Inc. Patents Durable Reflection-Controllable Electrochromic Thin Film Material for Windows

Start-up Soladigm, Inc (Milpitas, CA) earned U.S. Patent 7,646,526 for durable micrometer and nanometer active electrochromic thin-film material comprised of an alloy of antimony and one or more base metals. The transparent protective film is non-permeable to lithium, oxygen, and water.  The films may be as thin as 5 nanometers.  

The thin-film materials can be utilized in reflection-controllable electrochromic windows (i.e., light-control glass) for buildings, vehicles, aircraft and watercraft without using blinds or curtains, according to inventors Zhongchun Wang and Paul P Nguyen. 

The films can be used to make highly durable reflection-controllable electrochromic thin-film materials with an electrochromic active layer. The highly durable reflection-controllable electrochromic thin-film material are comprised of alloys of antimony and lithium.

Highly durable reflection-controllable electrochromic thin-film materials are comprised of a multilayer thin-film stack formed from antimony or antimony-lithium alloy and a base metal or a base-metal alloy.  Thin-film material of antimony, a base metal, and lithium, has survived cycling tests in an all-solid-state reflective device for over one hundred cycles with less than 10% of degradation in the switching ranges of both transmission and reflection.
Conventional electrochromic-based light-control glass, including tungsten-oxide-based versions control light by absorbing the light using a light-control layer. A significant drawback with absorbing the light is that heat is produced and radiated into a room when the light-control layer absorbs light, thereby diminishing the energy-saving effect of the conventional electrochromic light-control glass. To eliminate this drawback, another approach of reflecting light rather than absorbing light has been considered. Accordingly, a material capable of reversibly switching between a mirror state and a transparent state would be useful.

For a long time, such a material capable of switching between a mirror state and a transparent state was not found, but in 1996 a group in the Netherlands discovered a hydride of a rare earth, such as yttrium or lanthanum, switches between a mirror state and a transparent state under the influence of hydrogen. Such a material is conventionally referred to as a "switchable mirror"

Soladigm's thin film is formed from antimony, a base metal, and lithium and is produced in a well-known manner using a multi-source magnetron sputtering apparatus. The thin film is formed on a glass sheet. The glass sheet substrate was washed, placed in a vacuum apparatus, and then subjected to vacuum evacuation. The thin film that was deposited had a typical metallic gloss and was in a mirror state. 
When base metals, which are typically much less diffusive than noble metals, are added into the electrochromically active layer of a solid-state electrochromic device, the problems associated with electromigration in the solid-state electrochromic device are eliminated. That is, a thin-film material according to Soladigm's design does not exhibit electromigration when used in a solid-state electrochromic device.

The thin-film material becomes transparent upon lithiation and reflective upon delithiation. Additionally, a protective layer that is formed in a well-known manner from a material that is non-permeable to lithium, oxygen, and water can be optionally formed over the highly durable reflection-controllable electrochromic thin-film material developed by Soladigm. Examples of suitable materials for the protective layer include silicon oxide, aluminum oxide, silicon aluminum oxide, zirconium oxide, silicon carbide, and silicon oxycarbide. 

Soladigm is developing next-generation green building solutions with a global impact.  By bringing together a world-class team and resources from the glass, optical coatings, and semiconductor industries. Soladigm is funded by top-tier venture capital firms Khosla Ventures and Sigma Partners


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