Dynamic windows, which for electronic control of light and heat flow into and out of buildings, have advantages in both aesthetics and energy efficiency in buildings compared to static low-e coatings or mechanical shades.

Most traditional dynamic window technologies use electrochromic mechanisms such as electrochromic polymers and ion-intercalation metal oxides. Despite decades of research, these technologies have failed to drastically impact the market due to their inability to simultaneously achieve color neutral and fast switching at a low cost and large scale. They have been limited to niche applications such as in luxury cars and airplane windows.

In our group, we have developed a technology that can achieve the above stated metrics with a different approach: reversible metal electrodeposition. These windows use a transparent conducting oxide (TCO), nearly colorless metal salts dissolved in aqueous media, and a metal counter electrode. Upon holding a cathodic potential on the TCO, metal ions are reduced to form a metallic film across the entire the TCO, blocking out light. Holding an anodic potential will oxidize the metals back to their ionic form where they dissolve back into the aqueous electrolyte. The metal counter electrode acts as a source and sink for metal ions in the electrochemical cell.

Schematic of Dynamic Window based on Reversible Metal Electrodeposition

Recently, we have shown that we can achieve color neutral tinting with high shelf (>1 month) and cycle life (10,000 cycles) and the ability to produce a uniformly tinted window at scale (15 cm x 15 cm). These windows should also be substantially cheaper than alternatives due to simpler and more scalable processing techniques.

We are working on projects to continue increasing scale (~1 m x 1 m) and improving durability (ASTM E2141-14: 50,000 cycles at 85C, 85%RH and 1-sun UV illumination) of our dynamic windows.