Scalable and Durable Symmetric Electrochromic Devices via Zinc-Iodine Electrodeposition for Smart Window Applications

Electrochromic (EC) materials represent a class of highly promising smart materials, with the core advantage of dynamically modulating optical properties in response to an applied voltage. Although EC materials have evolved from transition metal oxides to ion-based electrodeposition films, their commercialization remains hindered by high costs and complex manufacturing processes. This study introduces a symmetric electrochromic device (ECD) based on Zinc and Iodine electrodeposition/dissolution, which demonstrates exceptional optical modulation performance. It features a minimalist structure consisting of two pristine TCO glass substrates sandwiching a single injected electrolyte without any pre-deposited electrodes. The device achieves a high optical modulation window of approximately 85% at 600 nm, exhibits rapid response time (reaching 90% of coloring/bleaching in just 4.7 s/3.9 s), and, most importantly, retains structural integrity over 30 000 cycles, retaining approximately 70% of the initial optical modulation. In addition, a large-area device (20 × 20 cm²) exhibits excellent color uniformity, demonstrating outstanding scalability and marking a major breakthrough in the development of EC smart windows.