A better-performing, longer-lasting “smart window” material
A large portion of the world’s energy expenditure is devoted to the heating, cooling, and lighting of buildings. Electrochromic materials are widely used to control the amount of light and heat allowed to pass through windows (i.e., “smart windows”). Traditional smart windows suffer from irreversible darkening, such that the transparency of the window can no longer be accurately controlled, if exposed to UV radiation, which is abundant in sunlight.
University of Texas researchers have developed an added blocking layer that prevents such darkening, improves cycling stability, and stabilizing the interface against electrochemical degradation, allowing for higher durability and decreased switching time for the transparency of smart windows.
The samples with the aforementioned blocking layer (orange and light blue lines) show much less irreversible darkening once exposed to UV light than the traditional smart window coating (dark blue line), showing their increased durability when subject to accelerated testing conditions. This superior resistance to irreversible darkening is owing to the blocking layer’s large electronic band gap and deep valence band edge leading to a considerable hole transfer barrier.