High-performance solid-state electrochromic device for emissivity control

This research presents a solid-state electrochromic device with exceptional emissivity control. The device's architecture includes thin films deposited on a glass substrate through magnetron sputtering: Au, NiO, Ta₂O₅, WO₃, and ITO. The NiO layer stores ions, while Ta₂O₅ serves as an ion-conducting and electron barrier layer, enabling ion intercalation within WO₃ upon voltage application. This process induces significant changes in optical properties. The device shifts from a high reflecting state (95% reflectance) to a low reflecting state (1% reflectance) under positive bias, relative to the Au electrode, at 660 nm. Importantly, a negative bias restores the original high reflectance. The device's standout features include a rapid reflectance modulation with high contrast and an average switching time of approximately 5 seconds. This switching time is a significant improvement compared to similar devices in previous studies. Furthermore, optimization of NiO and ITO layers during fabrication yielded resistivity in the range of a few milli-Ohms per centimeter (mΩ·cm). This optimization is the key to its exceptional performance. This study highlights the immense potential of the device in applications such as energy-efficient optical systems, thermal regulation, and emissivity-driven radiative cooling.