Ultra‐Stable Dual‐Band Electrochromic Windows Enabled by Shear‐Phase Niobium Oxide

ABSTRACT Dual‐band electrochromic windows (DEWs) enable selective modulation of visible (VIS) and near‐infrared (NIR) solar radiation, providing an effective strategy to reduce building energy consumption. Conventional electrochromic materials, however, undergo lattice distortion, interfacial stress, and irreversible phase transitions during repeated ion intercalation/deintercalation, which lead to rapid optical degradation. Herein, we report ultra‐stable DEWs based on shear‐phase Nb 2 O 5 with electronic‐structure engineering via W 6+ doping. The 2D shear‐phase framework suppresses phase transitions and volume expansion during cycling, while W 6+ substitution introduces oxygen vacancies and strengthens ion‐lattice coupling through d‐p orbital hybridization. The combination of structural and electronic optimization enhances electronic conductivity and reduces the ion diffusion barrier. As a result, W‐doped Nb 2 O 5 films achieve large optical modulation of 92.3% at 633 nm and 93.8% at 1200 nm, rapid switching (coloration/bleaching: 3.4/2.8 s at 633 nm and 2.4/5.2 s at 1200 nm), excellent bistability, and outstanding cycling stability, with less than 10% optical loss after 100 000 cycles. Simulations demonstrate that these DEWs offer substantial energy‐saving potential under diverse climates, and their integration with photovoltaic‐electrochromic systems enables self‐powered operation. This study establishes the first intrinsic stabilization mechanism for Nb 2 O 5 ‐based dual‐band electrochromism and provides a general design principle for durable, energy‐efficient smart windows.