Factors that Determine the Length Scale for Uniform Tinting in Dynamic Windows Based on Reversible Metal Electrodeposition

Dynamic windows based on reversible metal electrodeposition are attractive compared to conventional electrochromics because they can have neutral color, high contrast, and potentially lower cost, yet they are not nearly as developed, and the design rules for making them function at large scale are not presented in the literature. We model the voltage drops that occur in the transparent electrodes to get insight on how to obtain uniform electrodeposition of metals over large area. By optimizing the surface and density of the Pt nanoparticles used to nucleate metal growth, we lower the nucleation barrier for electrodeposition by 70 mV. We show that the growth rate of the metal films is determined by diffusion rather than reaction kinetics, which makes it possible to achieve uniform film deposition over a range of potentials from -300 to -700 mV. We demonstrate 100 cm(2) dynamic windows that are color neutral and tint uniformly from a clear state (>60%) to a dark state (<5%) in less than 1 min.