All solid state electrochromic devices based on the LiF electrolyte

The unsafe deposition process and slow deposition rate of the electrolyte layers are the main obstacles for electrochromic devices (ECDs) toward commercial application. In this work, an ECD with a structure of glass/ITO/WO₃/LiF/NiO/ITO has been prepared by electron beam and resistance evaporation methods. The LiF electrolyte is deposited by resistance evaporation with the LiF particles and shows promising potential as the Li⁺ based electrolyte in ECDs owing to its high transparency and good ionic conductivity. The ECD shows a fast response (4.0 s for bleaching and 9.6 s for coloring), large optical transmittance modulations (∼58.9% at 625 nm, 100 s for coloring), good stability and high coloration efficiency (88.5 cm² C^-1). This work not only indicates that LiF can be used as a Li⁺ based electrolyte in an ECD, but also paves a new way to fast and safe preparation of ECDs with high performance.