Solar and thermal dual-band electrochromic windows for energy-efficient buildings.

Windows mediate over 60% of solar gain (0.38‒2.5 μm) in summer and more than 40% of radiative loss (2.5‒20 μm) in winter. Traditional electrochromic (EC) smart windows can manipulate heat only in visible and near-infrared wavelength regions by adjustable transmission, while neglecting the thermal radiation of long-wave infrared emissivity (ɛLWIR). Here, we report a solar and thermal dual-band EC (STDEC) window that independently modulates solar transmission (∆Tsol = 52.2%) and ɛLWIR (∆ɛLWIR = 0.87) by integrating a dynamic copper-bismuth (Cu-Bi)-based reversible metal electrodeposition system with a spatial rotation architecture. Consequently, the STDEC window lowers summer daytime temperatures by up to 22.2 °C and raises winter nighttime temperatures by up to 1.5 °C versus normal glass in outdoor thermal tests. Furthermore, building energy simulations suggest that our window demonstrates higher year-round energy savings and thus global carbon dioxide (CO2) emission reduction. This STDEC window provides a sustainable pathway towards energy-efficient buildings.