Effect of Oxygen Content on the Properties of Sputtered TaOx Electrolyte Film in All-Solid-State Electrochromic Devices

Abstract

Tantalum oxide (TaOx) thin films are one of the commonly used solid electrolytes in inorganic all-solid-state electrochromic devices (ECDs). The chemical composition and microstructure of TaOx films have a crucial influence on its electron blocking and ion transport properties in all-solid-state ECDs. In this work, various oxygen flux was used to deposit the TaOx films with different compositions and microstructures by pulsed direct current (p-DC) reactive magnetron sputtering. The structural properties, morphologies, chemical compositions, optical properties, electron blocking, and ionic conductive properties of the TaOx films were systematically investigated. The results show that in a certain range, the higher the oxygen flux, the stronger the ion transport ability of TaOx and the lower the electronic conductivity, which could be attributed to the loose structure and smaller number of oxygen vacancies of the films, respectively. Moreover, an all-solid-state ECD with the multilayer structure of glass/ITO/WO3/Li/TaOx/NiO/ITO was also fabricated by the magnetron sputtering method. The device exhibited excellent comprehensive electrochromic properties including high optical modulation, large coloring efficiency, fast response (especially bleaching process), and good cycle stability.