Vapor–Liquid Transition‐Based Broadband Light Modulation for Self‐Adaptive Thermal Management

Abstract Considerable research efforts have aimed to control indoor temperatures to improve daily life and industrial production. However, current strategies, which involve active regulation of energy input or passive regulation of sunlight transmission, cannot control indoor temperatures under all weather conditions. Herein, a self‐adaptive thermal management device (STMD) that uses solar energy (heating) and radiative cooling (cooling) by exploiting the temperature differences across the device is reported. The adaptive heating and cooling functions are achieved by modulating sunlight transmittance and reflectance using a porous SiO₂ coating separated/merged with a refractive index‐matched liquid which serves as a shutter. As a result, the STMD in the opaque mode exhibits low transmittance and in the transparent mode exhibits sufficiently high solar transmittance. Taking advantage of this self‐regulated shuttering mechanism, the developed STMD enables i) an increase of ≈10 °C relative to the ambient temperature under a solar intensity of 400 W m⁻² in cold weather and ii) a temperature reduction of ≈5 °C under a solar intensity exceeding 900 W m⁻² in hot weather. The described design strategy offers an approach for constructing smart light‐controlling devices and thermal‐controlling building materials.