An Adaptive Solar Conditioning and Long-Wave Radiation Heat Management Smart Window for Energy Conservation

Radiative cooling materials leveraging spontaneous long-wave infrared emission into space are rapidly advancing, promising transformative impacts on global refrigeration. However, in regions with distinct seasons, more economical materials with the ability to modulate high LWIR emissivity are essential for achieving summer cooling and winter insulation. Furthermore, compared with inorganic materials, thermochromic smart windows based on hydrogel systems instantly became opaque, which is detrimental to daytime illumination and field of vision under nonextreme temperatures. To overcome this limitation, we engineered a thermochromic phase-change layer (broad temperature range from 32 to 50 °C) of poly(<i>N</i>-isopropylacrylamide) (PNIPAM) doped with conductive polyaniline gel, an integrated temperature sensor, and a modified T-MXene-dispersed high-emissivity gel. The precursor solution for the transparency-changing and high-emissivity gel was injected into a homemade model and polymerized in situ on both sides. Meanwhile, the transparent poly(4-methyl-1-pentene) (PMP, commercial name: TPX) and commercial low-E glass are used as the encapsulation materials. The prepared smart window enables high-contrast emissivity switching via mechanical flipping and gradually changes its transparency. This work offers valuable insights for advancing smart window design and paves the way for next-generation energy-efficient fenestration technologies.