Solid-State Nanocomposite Electrochromic Pseudocapacitors

We report on an electrochromic phenomenon in transition metal oxide materials induced by a novel mechanism involving charge/discharge of a solid-state electrochemical pseudocapacitor. Thin film nanocomposites of polycrystalline nickel oxide nanoparticles embedded in an amorphous tantalum oxide electrolyte matrix have been fabricated by reactive radio-frequency magnetron sputtering from a composite metal target followed by a oxygen anneal. Polycrystalline NiO nanoparticles within the composite play a role as an active electrochemical component while a surrounding amorphous matrix acts as a proton electrolyte. This unique nanocomposite material construction exhibits a substantial electrochromic optical modulation.