SrTiO3 enhanced high thermal conductivity and emissivity PVDF composite films for radiative cooling

When using high-power devices outdoors, especially in sunny summers, power losses coupled with direct sunlight can cause devices to overheat. This overheating not only disrupts their normal functioning but also increases the risk of fire accidents. To address this issue, the flexible polyvinylidene fluoride (PVDF)/strontium titanate (SrTiO₃, denoted as ST) composite films (abbreviated as P-S-x where x represents the mass ratio of PVDF to ST, x = 0.5, 1, 1.5, 1.75) were developed through a simple mixing method. Outdoor Radiant Cooling tests demonstrate that the P-S-1.75 sample exhibits an average cooling effect ∼14.2 °C compared with pure PVDF sample and an average cooling effect ∼20.2 °C compared with a bare Al sample. The P-S-1.75 sample with a thickness of 115 μm achieves exceptional performance in the broadband mid-infrared range from 2.5 to 25 μm with an average emissivity reaching about 97 %. And the max reflectance of P-S-1.75 sample reaches 90 % in the range of 0.5–2.0 μm. Furthermore, P-S-1.75 sample obtains a thermal conductivity ∼1.97 W/(m·K) which is about ten times higher than that of pure PVDF (0.2 W/(m·K)), and a cooling effect of 11.7 °C on the ceramic heating plate was obtained. The outstanding cooling performance exhibited by P-S-1.75 coating can be attributed to its exceptional radiative cooling capacity and high thermal conductivity. This work provides a new idea to obtain polymer/ceramic composite materials with excellent radiative cooling performance in cooling applications.