Electronically tintable windows increase the energy efficiency and comfort of buildings and automobiles. Recently, dynamic windows harnessing reversible metal electrodeposition have been explored as a viable alternative to electrochromic materials. In this manuscript, we first construct 25 cm 2 dynamic windows with two tin-doped indium oxide (ITO) working electrodes, a metal frame counter electrode, and an aqueous-based electrolyte containing metal ions. This arrangement allows metal electrodeposition to occur simultaneously on both window panes and increases switching speed such that devices switch to ∼30% transmission in 10 s compared to analogous windows with one working electrode which take 30 s to reach the same transmission value. Windows with two working electrodes switch between clear (∼82% transmission at 600 nm) and black (∼8% transmission at 600 nm) states within 30 s, making them among the fastest metal-based dynamic windows reported on this scale. Second, we elicit selective metal electrodeposition on Pt nanoparticles that are attached to ITO substrates via a self-assembled monolayer (SAM). By patterning the SAM of Pt nanoparticles, metal electrodeposition can be spatially controlled on both the macroscale and microscale. Taken together, these results demonstrate the versatility of the reversible metal electrodeposition architecture for dynamic windows.

Dynamic windows with electronically tunable transparency have applications in buildings, automobiles, and switchable sunglasses. By modulating solar lighting and heating flux, well-functioning dynamic windows improve the energy efficiency, comfort, and aesthetics of spaces. While most switchable windows utilize electrochromic materials, we have developed dynamic windows based on the reversible electrodeposition of metals. These windows possess clear-to-black transitions with ~80% optical contrast in 1 minute. 25 cm2 prototypes of these devices switch thousands of times without detectable deterioration. The windows function through the electrochemical movement of metal between a transparent conducting working electrode and a counter electrode metal frame. To facilitate uniform electrodeposition over a large working electrode area, transparent conducting oxides are modified with a self-assembled monolayer of Pt nanoparticles, which serves as an inert metal seed layer for metal nucleation and improves electrodeposit morphology. An aqueous electrolyte separates the two electrodes and consists of Ag+, Cu2+, Pb2+, and/or Bi3+ ions. We investigated several electrodeposition chemistries and established relationships between electrolyte composition and device performance. In addition, by selecting appropriate electrolyte additives, we have constructed dynamic windows that switch reversibly at temperatures as low as -40°C without electrolyte freezing. Lastly, we consider how improvements in electrode design will increase the scalability and optical functionality of these devices. Photograph of Mt. Rose, Nevada through a 25 cm2 dynamic window based on reversible metal electrodeposition as it switches in subfreezing weather: Figure 1