Electrochromic thin films of tungsten oxide with high-exposure (002) crystal faces doped and modulated with cerium acetate†

The electrochromic layer is the key part of the electrochromic device, and it is usually necessary to introduce nanomaterials or other functional materials to improve the response speed and stability. In this paper, a cerium acetate-doped tungsten oxide film (WO₃-CA) prepared by a hydrothermal and annealing method is presented and compared with a pure tungsten oxide film (WO₃) and an acetate-doped tungsten oxide film (WO₃-HAC) in terms of electrochromic performance. The electrochemical analysis results show that the Li⁺ diffusion rate of the WO₃-CA film is 37.36 × 10⁻¹² cm² s⁻¹, which is 2.6 and 2.2 times higher than that of pure WO₃ (14.21 × 10⁻¹² cm² s⁻¹) and WO₃-HAC (16.93 × 10⁻¹² cm² s⁻¹), respectively. Combined with density-functional theory (DFT) simulations, it was investigated whether the introduction of cerium acetate forms new Ce–O coordination bonds with oxygen atoms in WO₃ and exposes more (002) crystal faces. In addition, the introduction of acetate ions also contributes to the improvement of the structural stability and electrochemical properties of the films, which promotes the enhancement of the electrochromic effect. This mechanism provides a new idea for optimizing electrochromic materials.