Thermally-stable dynamic windows based on reversible metal electrodeposition from aqueous electrolytes

Dynamic windows based on the reversible electrodeposition of metals are a promising alternative to those utilizing electrochromic materials. In this manuscript, we develop 25 cm 2 dynamic windows based on the reversible electrodeposition of Cu and Bi from aqueous gel electrolytes that switch with a contrast ratio of ∼80% in one minute. Although the aqueous electrolyte promotes rapid and uniform metal electrodeposition, its narrow operable temperature range limits practical implementation of the devices. To overcome this issue, we employ additives that prevent electrolyte freezing while still allowing for reversible metal electrodeposition. With properly-selected antifreezes that do not bind strongly to metal ions, the windows switch reversibly at temperatures down to −40 °C. The enhanced thermal stability of these systems is necessary for the practical implementation of metal-based dynamic windows. Appropriate additives to dynamic windows based on reversible metal electrodeposition allow aqueous-based electrolytes to be used that support minute-long switching times across a wide temperature range.