Fig. 1: Design of AACP.
a Net cooling power as a function of ambient temperature for various R̅solar. Theoretical calculation is based on steady state heat transfer balance analysis (details in Method). Subambient cooling is difficult to achieve when R̅solar < 0.9 even if the material has a perfect \({\bar{\varepsilon }}_{{{{{{\rm{LWIR}}}}}}}\). b The scattering efficiency of a single TiO2 spherical particle as a function of particle diameter over wavelength range of 0.3 to 2.5 µm in different scattering mediums. c Simulated reflectance curves and resulted R̅solar values as a function of TiO2 nanoparticles (NPs) packing density (ϕ) for a film of 2 µm thickness. The declining trend of reflectance in the dashed circle is due to the dependent scattering effect from particle crowding. d Relationship between apparent water contact angle (θapp) and the intrinsic Young’s contact angle (θY) of TiO2 surfaces. e Anticipated R̅solar and θapp as a function of ϕ resulting from f the three proposed regimes: I, II, and III. A trade-off between the R̅solar and θapp renders regime II as the design target to obtain excellent radiative cooling and anti-soiling performances at the same time. The degree of dependent scattering adds complexity to anticipate the variation of R̅solar when ϕ is high. Therefore, in e, the dashed line of the solar reflectance data curve only indicates a possible variation trend.
