Self-Adaptive Smart\nThermochromic Film with Quick\nResponse for All-Year Radiative Cooling and Solar Heating

The advancement of energy-saving buildings requires both\nhigh-performance\npassive radiative cooling (PRC) and solar absorption heating (SAH)\nmaterials. Although many materials with PRC or SAH functions have\nbeen developed, they cannot adapt to the large fluctuations of ambient\ntemperature in different seasons. Herein, we report the design and\nfabrication of a new thermochromic porous film (TMRC) with combined\ntemperature-adaptive SAH and PRC performance to achieve “warm\nin winter and cool in summer” for all-year radiative cooling\nand solar heating. The porous structure and embedding thermochromic\nparticles endow the TMRC with an ultrawide modulation capability for\nsolar reflectivity ranging from 86.1% to 13.3% and a reversible color\nchange in response to temperature variation. When the ambient temperature\nexceeds the transition temperature (<i>T</i><sub>c</sub> = 22 °C), TMRC enters a radiative cooling mode. At temperatures\nbelow the <i>T</i><sub>c</sub>, TMRC heats up by 6.5 °C\nin cold winter due to its high solar absorptivity. TMRC exhibits a\nrapid response time of 40 s at near room temperature. Compared to\ntraditional cement coatings, TMRC can reduce energy consumption up\nto 38.05 kWh/m<sup>2</sup> (18%) in midlatitude regions according\nto energy consumption simulations. In addition, TMRC shows excellent\nself-cleaning and UV-aging resistance abilities. Therefore, this work\nprovides a low-cost and scalable technique for reversible TMRC for\nall-year-efficient thermal management.