(133d) Making Smart Windows Smarter

Transparent solar cells that exclusively harness UV photons can provide on-board power for electrochromic windows to regulate visible and infrared light transmission without competing for the same spectral irradiance. With more than 40% of national electricity consumption attributed to heating, cooling, and lighting in commercial and residential buildings, this solar cell technology can unlock new markets for electrochromic windows, simultaneously rendering energy savings, reducing carbon emissions, and increasing occupant comfort. The ability to provide onboard power obviates the need for external wiring, which should dramatically decrease installation costs and increase window operability. Starting with the design and synthesis of molecular chromophores possessing wide bandgaps, we recently constructed and tested such UV-absorbing solar cells, and demonstrated their utility in powering electrochromic windows. This technology was highlighted in the Wall Street Journal as “smart windows that can be sunglasses for [one’s] house.”

In this talk, I will highlight this self-powered smart window technology, focusing on the development of the UV-absorbing solar cells. The use of wide bandgap chromophores has allowed us to exclusively harvest near UV light, leaving visible light and infrared heat to be regulated by the electrochromic window. A necessary consequence of using wide bandgap chromophores is that our solar cells produce high-voltage, low-current power. Coupled with pinhole- and defect-free active layers, this inherently low-loss power production is scalable with the footprint of the solar cells. In our prototype, the energy that is produced by the solar cell in an hour exceeds more than ten times the energy that is required to power the electrochromic window over a 24-hour period. With a simple storage device that trickle charges the electrochromic window, light transmission can be regulated in the evenings and on cloudy days, independent of solar insolation.