Dual Tinting Dynamic Windows Using Reversible Metal Electrodeposition and Prussian Blue

Electronically tintable windows based on reversible metal electrodeposition are a promising alternative to electrochromic materials due to the high optical contrast imparted by the opacity of thin metal films. While traditional metal-based dynamic windows utilize a metal counter electrode frame, metal electrodeposition on the working electrode must be paired with a plane-parallel counter electrode that facilitates transverse ion migration to enable uniform metal electrodeposition on a large scale. In this manuscript, we develop dynamic windows that combine reversible Bi electrodeposition on the working electrode with a Prussian blue counter electrode that acts as both a charge storage layer that intercalates K+ ions and an anodically coloring material. Since both electrodes darken during window tinting, 25 cm2 devices switch with an optical contrast of ∼67.5% at 700 nm in only 3 s, making them the fastest dynamic windows using reversible metal electrodeposition reported on this scale.