Chromogenic materials for transmittance control of large-area windows

Abstract

Chromogenic materials have optical properties that can be changed in a persistent and reversible manner under the action of an external stimulus. They can regulate the throughput of radiant energy between widely separated extrema, and hence they can be used in future “smart windows” in buildings, cars, etc., and for many other applications. This article summarizes the state-of-the-art for:

• Photochromic (light sensitive) materials, with a focus on glass and spirooxazine compounds

• Thennochromic (temperature sensitive) materials, particularly vanadium-oxide-based coatings and “cloud gels”

• Electrochromic (electric charge dependent) materials integrated in multilayer configurations, with emphasis on transition metal oxide coatings and ion intercalation into these

• Certain liquid-crystal-based (electrically switched) materials of the guest-host as well as the polymer dispersed and encapsulated types