Smart windows are windows whose transparency can be tuned between the transparent and opaque state by an electrochromic system. A variety of materials are used, e.g., electrochromic materials and liquid crystals (LCs). Optically switchable LCs can switch between the transparent and opaque state by utilizing light at specific wavelengths. This is highly beneficial, as the window automatically changes between transparent and opaque state depending on the ambient light condition.
Doo-Hyun Ko, Korea Institute of Science and Technology (KIST), Seoul, South Korea, and colleagues created an even smarter window by combining a transparent, dye sensitized solar cell (DSSC) with an optically turnable LC layer. Depending on UV light, the device switches from a transparent, energy-harvesting mode (so-called day mode) to an opaque and inactive state (night mode).
The switch from night to day mode is achieved after exposing the device to a solar simulator for 60 s, resulting in a photovoltaic performance of 1 to 7 %, meaning that solar energy can be collected during the day. In night mode, which is triggered by the absence of UV light, the device ensures privacy and security by the opaque state of the window.
- Optically Switchable Smart Windows with Integrated Photovoltaic Devices,
Hyun-Keun Kwon, Kyu-Tae Lee, Kahyun Hur, Sung Hwan Moon, Malik M. Quasim, Timothy D. Wilkinson, Ji-Young Han, Hyungduk Ko, Il-Ki Han, Byoungnam Park, Byoung Koun Min, Byeong-Kwon Ju, Stephen M. Morris, Richard H. Friend, Doo-Hyun Ko,
Adv. Energy Mater. 2014.