Flexible Normally Transparent Smart Window Modulating Near‐Infrared Penetration under Ambient Conditions

Abstract Smart windows that both reversibly occlude visible light and modulate the penetration of near‐infrared (NIR) light save a great deal of energy. Here, a simple, super‐fast, electrically switchable smart window that initially reflects NIR light and then scatters it in response to thermal stimuli is designed and fabricated. Transparent polymer‐stabilized cholesteric liquid crystals (PSCLCs) are prepared by photo‐polymerizing RM 257 monomers in which the planar CLCs fully reflected NIR light (1050–1550 nm). Next, an ultra‐thin, thermotropic, W_0.003V_0.997O₂‐doped polyvinylpyrrolidone hybrid thin layer that modulates NIR light penetration over a very broad temperature range is overlaid on the PSCLCs, and the final WVO‐PSCLCs smart window features four NIR modulation modes. Specifically, when a model wood house with three 1.5‐ × 2‐cm WVO‐PSCLCs smart windows is thermally irradiated by a 250‐W infrared light for 10 min, the internal temperature is 4.8 °C less than that of a house lacking smart windows. Flexible smart windows fabricated from polyethylene terephthalate (PET) could be bent through a radius of 15 mm without any noticeable damage, and are very resistant to external vertical pressure. The flexible WVO‐PSCLCs smart windows are versatile, and afford outstanding transparency management and modulation of NIR light penetration.