Pulsed electrodeposition for dynamic windows based on reversible metal electrodeposition

Abstract

Dynamic windows based on reversible metal electrodeposition electronically tint and bleach, enabling user control of light into and out of buildings. The operating mechanism is to reversibly electrodeposit a thin layer of metal (e.g., Cu and Bi) onto a transparent conductor to block light. Tinting to a desired opacity is constrained by a rough film morphology using direct current (DC) electrodeposition, limiting window switching speed. Here, we show that smoother films can be grown with pulsed electrodeposition with a 10% duty cycle and 1-Hz frequency because ions are able to diffuse past protrusions during the rest phase. While these films initially tint slower compared to DC plating, the films using this pulsing protocol reach 0.1% transmittance 45% faster. Finally, we show that pulsing enables consistent optical properties of dynamic windows after 2,400 cycles due to effective suppression of dendrite growth on the metal mesh counter electrode.