Recent progress in thermochromics and electrochromics: A brief survey

Contemporary architecture is characterized by large glazings, which are able to accomplish good indoors-outdoors contact and daylighting. However, glazings, encompassing windows and glass facades, are challenging with regard to energy efficiency and often lead to excessive solar energy ingress and to large thermal losses, which must be balanced by energy-demanding cooling or heating. Cooling, especially, has grown strongly in importance during recent years. Emerging technologies utilizing thermochromics and electrochromics allow control of the inflow of visible light and solar energy and thereby produce better energy efficiency than traditional glazings employing static solutions. Thermochromic thin films, based on vanadium dioxide, let through less solar energy at high temperature than at low temperature, whereas electrochromic devices include thin films-usually based on tungsten oxide and nickel oxide-that can change their transmittance of solar energy and visible light upon the application of a voltage. It is important that electrochromics, and to some degree thermochromics, can enhance indoor comfort and lead to better living and working conditions. The present brief review covers a number of recent advances in thermochromics and electrochromics with a view to applications in energy-efficient buildings.