Electrochromics - History, technology, and the future

This paper begins with the history of electrochromism, first discovered in the 1880's. The physics, electrochemistry, device design and materials are covered. The science of electrochromism involves the coloration of a variety of metal oxides, organics and polymers. Dual ion and electron intercalation is used to color and bleach electrochromic materials. Considerable science has been undertaken to make devices that resemble thin film transparent batteries in their structure. A number of materials have been developed to make layers for electrochromic devices. Applications for electrochromics include low information content displays, such as banner displays, smart windows and mirrors for automotive applications. Several companies throughout the world are developing dynamic glazing. Switchable glazing for building and vehicle application is very attractive for energy and light management. From the standpoint of materials much research and development in electrochromics focuses on the development or improvement of materials with ionic and electronic properties. Much of the work on electrochromics draws on the vast knowledge developed for advanced batteries. National Laboratory and university groups are researching new materials and processes to improve electrochromic materials. Also, much industrial work is directed towards deposition and fabrication processes for glass and possibly plastic that can make electrochromics cost effective. Plastic can yield both flexibility and weight savings for many applications. Although plastics are permeable, outgas and require lower processing temperatures they can be more universally applied Some developments in plastics may come from OLED sealing technology. Comparisons are made between the properties of electrochromics and other switchable technologies. Technology comparisons are made between suspended particles, polymer dispersed liquid crystals, themotropics and gas-chromics.