Electrochromic devices (ECDs) can regulate the indoor solar radiation by adjusting optical transmissive properties, showing great commercial potential and important social value of green energy saving. However, the unsafety and high cost of Li⁺ based electrolyte hinder the large-scale and industrialized production of ECDs. Other metal ions have been used as electrolyte ions, but they are rarely reported in all solid state ECDs. In this study, MgF₂ film is used as the solid electrolyte to construct all solid state ECD with the structure of glass/ITO/WO₃/MgF₂/NiO/ITO. The ECD shows the large optical modulation (∼83% at 820 nm, with 100 s durations) and fast response (19.2 s for bleaching and 8.3 s for coloring, with 25 s durations). Moreover, the ECD achieves the extreme transmittance value of colored states Tc ≈ 0%, which can give an absolute private state. This work not only indicates that MgF₂ film can be an alternative to Li⁺ based electrolyte in all solid state ECDs, but also broadens the applications of all solid state EC smart windows to private buildings.

电致变色器件（ECD）可以通过调节光透射特性来调节室内太阳辐射，显示出巨大的商业潜力和绿色节能的重要社会价值。然而，Li ⁺基电解液的不安全性和高成本阻碍了ECD的规模化和工业化生产。其他金属离子已被用作电解质离子，但它们在所有固态 ECD 中的报道很少。本研究以MgF ₂薄膜为固体电解质，构建了玻璃/ITO/WO ₃ /MgF ₂结构的全固态ECD/氧化镍/氧化钛。ECD 显示出较大的光学调制（在 820 nm 处约为 83%，持续时间为 100 秒）和快速响应（漂白为 19.2 秒，着色为 8.3 秒，持续时间为 25 秒）。此外，ECD 实现了有色状态 Tc ≈ 0% 的极端透光率值，可以给出绝对的私有状态。这项工作不仅表明 MgF ₂薄膜可以替代所有固态 ECD 中的Li ⁺基电解质，而且还拓宽了全固态 EC 智能窗户在私人建筑中的应用。