High-entropy rare-earth cesium tungsten bronze ceramic films that enable high-NIR shielding and visible transparency for smart windows

Thermochromic smart windows offer significant energy savings because they dynamically modulate solar radiation. Here, we report the first synthesis of rare earth-based high-entropy Cs 3x Nd x Sm x Tb x Dy x WO 3 (x = 0.022) nanoparticles via a hydrothermal reaction. By integrating these materials with poly(N-isopropylacrylamide) (PNIPAM) hydrogels, we fabricated a novel light/heat dual-responsive Cs 3x Nd x Sm x Tb x Dy x WO 3 /PNIPAM smart window. The high-entropy strategy increased the W 5+ concentration and the number of oxygen vacancies via entropy-driven stabilization, thereby suppressing the W 5+ oxidation process and significantly increasing the amount of near-infrared (NIR) absorption. Consequently, the Cs 3x Nd x Sm x Tb x Dy x WO 3 /PVA film achieved exceptional performance: 84.8% visible light transmittance (T vis ) and 94.4% NIR shielding (at 1500 nm). The integrated Cs 3x Nd x Sm x Tb x Dy x WO 3 /PNIPAM smart window improved the NIR rejection rate to 99.9% while maintaining a high T vis value. Crucially, outdoor testing demonstrated a 10 °C reduction in the indoor temperature at noon relative to that of standard quartz glass. The composite exhibited excellent cyclability and retained stable thermochromic switching and optical properties over repeated cycles, thus confirming its long-term durability. This entropy engineering approach fundamentally optimizes the electronic structure of tungsten bronze, thereby simultaneously enabling high visible transparency and ultrastrong NIR rejection. Our work establishes a promising pathway for the construction of next-generation smart windows with superior energy-saving performance.