Controlling Light Transmission: Recent Developments in Smart Windows at SWITCH Materials Inc., Dr. Glen Bremner

Dynamic glazing (commonly called smart windows) is a technological field focused on modulating light transmission through windows to improve occupant comfort, increase privacy, or prevent photodegradation. Depending on the technology, the change in transmission will be triggered by different stimuli, such as light (photochromism), temperature (thermochromism), and electricity (electrochromism). Founded on research at Simon Fraser University, SWITCH Materials is developing a dynamic sunroof glazing product to address the issue of solar heat gain in vehicles. The technology is based on diarylethene molecules, which exhibit a hybrid electrochromic-photochromic response. Sunlight induces a ring-closing reaction of the diarylethene molecule to its more deeply-coloured isomer. Electrochemical oxidation of the ring-closed isomer triggers a ring-opening reaction, returning the molecule back to its original, less-coloured state. The hybrid response makes SWITCH Materials’ technology uniquely suited to the automotive market. Passive darkening of the sunroof in response to sunlight helps minimize solar heat gain, such as when the vehicle is parked on a sunny day. The ability to light the film by applying a low voltage enables the user to control the amount of light entering the vehicle cabin on demand.