Self-Adaptive Smart Thermochromic Film with Quick Response for All-Year Radiative Cooling and Solar Heating

The advancement of energy-saving buildings requires both high-performance passive radiative cooling (PRC) and solar absorption heating (SAH) materials. Although many materials with PRC or SAH functions have been developed, they cannot adapt to the large fluctuations of ambient temperature in different seasons. Herein, we report the design and fabrication of a new thermochromic porous film (TMRC) with combined temperature-adaptive SAH and PRC performance to achieve "warm in winter and cool in summer" for all-year radiative cooling and solar heating. The porous structure and embedding thermochromic particles endow the TMRC with an ultrawide modulation capability for solar reflectivity ranging from 86.1% to 13.3% and a reversible color change in response to temperature variation. When the ambient temperature exceeds the transition temperature (T_c = 22 °C), TMRC enters a radiative cooling mode. At temperatures below the T_c, TMRC heats up by 6.5 °C in cold winter due to its high solar absorptivity. TMRC exhibits a rapid response time of 40 s at near room temperature. Compared to traditional cement coatings, TMRC can reduce energy consumption up to 38.05 kWh/m² (18%) in midlatitude regions according to energy consumption simulations. In addition, TMRC shows excellent self-cleaning and UV-aging resistance abilities. Therefore, this work provides a low-cost and scalable technique for reversible TMRC for all-year-efficient thermal management.