Azerbaijan National Academy of Sciences

Controlling lighting and heating through the use of dynamic windows substantially decreases the energy consumption of buildings. Currently, dynamic windows are commercialized on only a small scale due to problems associated with durability, color, switching speed, and cost. Most dynamic windows utilize electrochromic materials, which change their transmission properties upon application of a voltage. The vast majority of research on dynamic windows over the past four decades has focused on transition metal oxides or polymeric materials as electrochromic materials. The use of metals, which are excellent attenuators of visible light, as the optically active material in dynamic windows is an intriguing, yet little explored alternative approach. In this work, we construct robust dynamic windows that possess neutral color, high contrast, and excellent durability based on the uniform reversible electrodeposition of metals.

Dynamic windows, which switch between transparent and opaque states upon application of a voltage, have applications in buildings, automobiles, and switchable sunglasses. Here, we describe dynamic windows based on the reversible electrodeposition of Cu and a second metal on transparent indium tin oxide electrodes modified by Pt nanoparticles. Three-electrode cyclic voltammetry experiments reveal that the system possesses high Coulombic efficiency (99.9%), indicating that the metal electrodeposition and stripping processes are reversible. Two-electrode 25-cm2 windows without bus bars uniformly switch between a transparent state (∼80% transmission) and a color-neutral opaque state (<5% transmission) in less than 3 min. These devices switch at least 5,500 times without degradation of optical contrast, switching speed, or uniformity. Taken together, these results indicate that dynamic windows based on reversible metal electrodeposition are a promising alternative to those using traditional electrochromic materials.