Smart Glass: Making the Future Less Bright
By Jennifer Garland, Applied Physics, 2021
This article was originally published as part of Issue 34: Color.
The end may be near for finicky window blinds as more research funds the development of electrochromic devices. Electrochromism is the phenomenon of a material changing color due to the application of an electric potential. This voltage spurs electron transfer in a redox reaction, which alters the reflection and transmission of light through the material. With few limits to the size or shape of a devices’ displays, endless applications in architecture, transportation, and electronics are possible.
A promising innovation of electrochromic devices is the introduction of “smart glass” windows into homes and larger buildings. These windows switch from being transparent to opaque by applying only a small amount of power to sustain a darker appearance. An everyday example is the nighttime tinting of a car’s rear-view mirror; however, this technology has the potential to be used on a much wider scale. Smart glass use has been increasing in recent years and has a projected market growth of nearly 900 million dollars by 2022. Consequently, wide-scale use would greatly reduce energy consumption and air conditioning costs by filtering the electromagnetic spectrum to block light and heat.
These windows switch from being transparent to opaque by applying only a small amount of power to sustain a darker appearance.
The optical characteristics of smart glass are attributed to its layered structure, consisting of a glass substrate and transparent electrode bordering each side of an electrochromic mixture, most commonly tungsten oxide (WO3). The metal oxides used in the electrochromic mixtures produce shades of blue, gray, and black with varying voltages. The composition is essentially a rechargeable electrochemical cell that alters the optical properties of the affected material.
Although the battery-like structure of electrochromic devices in smart glass makes them more expensive and complicated to install than normal windows, large-scale use is still on the horizon with more development and public interest. Until then, curtains will have to do when glass being clear is just too inconvenient.
