Dynamic Windows with Neutral Color, High Contrast, and Excellent Durability Using Reversible Metal Electrodeposition

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-cm(2) windows without bus bars uniformly switch between a transparent state (similar to 80% transmission) and a colorneutral opaque state (<5% transmission) in less than 3min. 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 reversiblemetal electrodeposition are a promising alternative to those using traditional electrochromic materials.