All-Solid-State Transparent Variable Infrared Emissivity Devices for Multi-Mode Smart Windows

Smart windows that incorporate photothermal modulators (PMs) can independently regulate solar transmittance and infrared (IR) emissivity to improve building comfort and reduce energy consumption. Herein, a novel all-solid-state variable IR emissivity device (VED) is first designed and fabricated with a high visible irradiation transmittance ( T ′ vis = 0.79) and solar irradiation transmittance ( T ′ sol = 0.75) using an ITO/SiO 2 /ITO Fabry–Perot cavity structure. The VED exhibits different IR emissivity (ɛ) values at positive (ɛ P = 0.80) and negative (ɛ N = 0.38) bias, allowing for dynamic regulation of radiation by controlling the electrical conductivity of the indium tin oxide (ITO) layer. Furthermore, an all-solid-state PM with a structure of ITO/SiO 2 /ITO/Glass/ITO/NiO/ZrO 2 /Li/WO 3 /ITO, which is capable of independently regulating solar transmittance (Δ T' sol = 0.31) and IR emissivity (Δɛ 2.5–25 µm = 0.42), is fabricated. The multi-mode smart window incorporating PMs can achieve “bright,” “dark,” “warm,” and “cool” modes, making them suitable for deployment in diverse climate zones. The innovative smart window holds a massive potential for use in reducing building energy consumption.