A Single‐Layer Thermochromic Film for Switchable Radiative Cooling and Solar Heating

Abstract Passive radiative cooling has garnered significant interest as a clean and sustainable cooling strategy. However, addressing the issue of overcooling at low temperatures remains a challenge. In this study, we designed a single‐layer thermochromic film for adaptive thermal management, which consists of a PDMS matrix, SiO 2 microparticles, TiO 2 nanoparticles, and thermochromic microcapsules. Thermochromic microcapsules enable passive switching between solar heating and radiative cooling by modulating their visible spectra in response to temperature fluctuations. SiO 2 microparticles are used to enhance thermal emission within the atmospheric transparent window, whereas TiO 2 nanoparticles are chosen for strong solar reflection. After comparing several samples, the optimal mass ratio of PDMS:TiO 2 :SiO 2 :thermochromic microcapsules is set as 1:0.8:0.1:0.1. Dynamic spectra measurements verify that the thermochromic film modulates visible light reflectivity from 0.94 to 0.81 as temperature decreases from 35 to 20 °C. Outdoor testing indicates that the film provides a 1 °C increase in cold conditions and a 2 °C decrease in hot conditions.