Near‐Infrared‐Activated Thermochromic Perovskite Smart Windows

Perovskite-based thermochromic smart windows that can change color have attracted much interest. However, the high transition temperature (>45 °C in air) hinders their practical application. Herein, a near-infrared (NIR) activated thermochromic perovskite window that enables reversible transition cycles at room temperature is proposed. Under natural sunlight (>700 W m-2 ), it efficiently harvests 78% NIR light to trigger the thermochromism of perovskites, blocking the heat gain from both the visible and NIR light. Meanwhile, it also exhibits a low mid-infrared emissivity of <0.3, suppressing thermal radiation to the indoor environment. A field test demonstrates that this smart window can reduce the indoor temperature by 8 °C compared to a normal glass window at noon. The near-room-temperature color change, multispectral thermal management, outstanding energy-saving ability, and climate adaptability, and solution-based process of this window make it unique and promising for real applications.