Dual-Functional WO₃ Nanocolumns with Broadband Antireflective and High-Performance Flexible Electrochromic Properties

The three-dimensional, high-porous, and oriented WO₃ nanocolumn film with broadband antireflective and high-performance flexible electrochromic dual-functionalities is achieved by utilizing a simple, one-step, room-temperature glancing angle deposition without any catalysts and templates. It is found that the WO₃ nanocolumn film is effective in increasing the optical transparency in the visible range, enhancing the color-switching response time as well as improving the mechanical flexibility and electrochemical cycling stability in comparison to dense WO₃ film. The further optical, morphological, and electrode reaction kinetics analyses reveal that these improvements can be attributed to its unique porous nanocolumn arrays, which reduce the refractive index, facilitate the interfacial charge-transfer and ion-penetration, and alleviate the internal stress of the film under the bending treatment. These results would provide a simple and effective guidance to design and construct low-cost, robust, flexible, stable, and transparent electrochromic smart windows.