Surface modification of rare earth Sm-doped WO films through polydopamine for enhanced electrochromic energy storage performance.

Electrochromic materials (ECMs) could exhibit reversible color changes upon application of the external electric field, which exhibits huge application prospects in smart windows, energy storage devices, and displays. For the practical application of ECMs, the fast response speed and long cyclic stability are urgent. In this work, the nanoporous Sm-doped WO (WSm) films were constructed using hydrothermal technology, then polydopamine (PDA) was modified on the surface of WSm film to obtain the WSm/Px (x = 0.25, 0.5, 1.0, and 2.0) hybrid films. WSm/Px hybrid films displayed high optical contrast and large areal capacitance. In addition, in comparison with WSm film, the WSm/Px hybrid films exhibited faster response speed and better cyclic stability because PDA film enhanced the interface ion transport ability and electrochemical structural stability of the nanoporous WSm film. Notably, the WSm/P1.0 hybrid film displayed the colored/bleached times of 7.4/2.9 s, retained 90.2% of the primitive optical contrast (68.5%) after 5000 electrochromic cycles. Furthermore, the areal capacitance of WSm film could be increased by 224% through the modification of the PDA. Therefore, WSm/Px hybrid films are great prospects for electrochromic energy-saving and storage windows.