Sunlight-driven photo-thermochromic hybrid hydrogel with fast responsiveness and durability for energy efficient smart windows

Smart windows, which automatically regulate the intensity of sunlight entering the building, have attracted tremendous interest in solving the fast-approaching energy crisis by suppressing unnecessary energy usage such as cooling or heating. However, the switching behavior of conventional thermochromic smart windows are usually triggered by external heating. Herein, a novel fully autonomous photosensitive smart window that responds to the intensity of sunlight as well as the ambient temperature was constructed by using the thermo-sensitivity of PNIPAm and the photothermal effect of PDAPs. This obtained smart window enables photo-thermochromism driven by sunlight intensity, which preferentially triggers the smart window when the ambient temperature is lower than the hydrogel's LCST, resulting in cooler indoor temperatures and more comfortable living environment. Moreover, the smart windows designed in this work exhibit fast optical switching, excellent sunlight-induced solar modulation, high repeatability, and high durability, which are meaningful for further development of energy efficient smart windows.