Bio‐Inspired Ordered <scp> WO ₃ </scp> Nano‐Helixes Enable Multi‐Band Electrochromic Smart Windows with Ultrafast Switching and Robust Cyclability

Multi‐band electrochromic (MBEC) smart windows, capable of dynamic and selective management of solar radiation (visible and near‐infrared transmittance) and thermal radiation (mid‐ and long‐wave infrared emissivity), are crucial for zero‐energy buildings and adaptive optical systems. However, they have not yet been developed due to the inherent material design challenges and kinetics‐stability trade‐offs. Inspired by lotus root vessels, we develop vertically aligned nano‐helix tungsten oxide (NH‐WO 3 ) films with amorphous‐crystalline heterophase. The multiscale microstructure provides numerous active sites, enhances local electric fields, and alleviates stress during repeated cycling. Consequently, NH‐WO 3 achieves unprecedented quad‐band electrochromic performances with multi‐mode photothermal modulation across the visible to long‐wave infrared spectra, featuring large optical contrast (Δ T VIS–NIR ~79%), significant temperature and emissivity variation (Δ T = 9.3 °C, Δ ε = 0.47@5 μm), ultrafast switching (3.9/1.9 s@780 nm, 2.8/2.5 s@990 nm), and robust cyclability (10 000 cycles with only 9.1% optical‐contrast loss). Furthermore, a prototype smart window based on the NH‐WO 3 film maintains a comfortable indoor temperature of 26 °C even under continuous AM 1.5G solar irradiation for 1 hour. This bio‐inspired nano‐helix design provides an efficient strategy for the development of advanced next‐generation photothermal management smart windows toward practical energy‐efficient architectures and adaptive optics.