Switchable passive radiative cooling (PRC) smart windows can modulate sunlight transmission and spontaneously emit heat to outer space through atmospheric transparent window, presenting great potential in building energy conservation. However, realizing stable and on‐demand control of the cooling efficiency for PRC materials is still challenging. Herein, an electro‐controlled polymer‐dispersed liquid crystal (PDLC) smart window showing PRC property is designed and prepared by adding mid‐infrared emitting reactive monomers into the conventional PDLC matrix. It is found that not only the electro‐optical properties but also the PRC efficiency of PRC PDLC film are tunable by regulating the content of the mid‐infrared emitting components, film thickness, and micromorphology. This advanced PRC PDLC material achieves a near/sub‐ambient temperature when the solar irradiance is below 400 W m−2 and can dynamically manage daytime cooling efficiency. Importantly, its PRC efficiency is capable of being tuned in an on‐demand and ultrafast millisecond‐scale way, whose controllable transparency enables multistage heat regulation. This study is hoped to provide new inspiration in the preparation of advanced optical devices and energy‐efficient equipment.

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