Tungsten trioxide (WO₃)-based electrochromic devices have attracted great interest in smart windows, low-power displays, and other cutting-edge fields. The electrochromic behavior of WO₃ is strongly dominated by both electron conduction and ion diffusion process. Nevertheless, the structure–activity relationship of the WO₃ in the electrochromism has not been well elucidated so far. Herein, we systematically studied the relationship between the crystal structure composed of the fundamental units of typical WO₃ and the electron conduction/ion diffusion processes at a sub-nanoscale level. Our theoretical results unveil that the h-WO₃ with appropriate band gap by piling up the WO₆ octahedral molecular units along c axis profit electron conduction, and the continuous three-, six-ring tunnels along ab plane built by the units are conducive to ion diffusion. Therefore, the h-WO₃ film exhibits large optical modulation (up to 86% at 633 nm and 90% at 1000 nm), excellent cycling stability (86.4% of retention over 3000 cycles), and fast switching speed (1.9 s of bleaching time at 633 nm). Moreover, we provide unique insights between H⁺ adsorption/desorption and the electrochromic response in the near-infrared region. We believe that this study lays a foundation for the design and construction of high-performance electrochromic nanomaterials and broadband tunable smart windows.

三氧化钨（WO ₃）基电致变色器件在智能窗、低功耗显示器等前沿领域引起了人们的极大兴趣。_{WO 3}的电致变色行为主要受电子传导和离子扩散过程的支配。然而，迄今为止，WO ₃在电致变色方面的构效关系尚未得到很好的阐明。_{在此，我们系统地研究了典型WO 3}基本单元组成的晶体结构与亚纳米级电子传导/离子扩散过程之间的关系。我们的理论结果表明，通过堆积WO ₆可以得到具有适当带隙的h-WO ₃沿c轴的八面体分子单元有利于电子传导，其沿ab平面构建的连续的三、六环隧道有利于离子扩散。因此，h-WO ₃薄膜表现出大的光学调制（在633 nm处高达86%，在1000 nm处高达90%）、优异的循环稳定性（3000次循环后保持率86.4%）和快速切换速度（1.9 s的漂白） 633 nm 处的时间）。此外，我们还提供了 H ⁺吸附/解吸和近红外区域电致变色响应之间的独特见解。我们相信这项研究为高性能电致变色纳米材料和宽带可调智能窗的设计和构建奠定了基础。