Optimizing the thermal conductivity and spectral selectivity of PVDF-based emitter for efficient radiative cooling

Radiative cooling technology has gained significant attention in building, clothes, and more, by increasing the sunlight reflectance and infrared emittance primarily. Despite the potential of passive radiative cooling in buildings, a key challenge is that materials with low in-plane thermal conductivity would create a thermal barrier, thus impeding the heat dissipation. To address this challenge, we developed a radiative cooling emitter using a scalable blade-coating technique. The emitter consists of a polyvinylidene fluoride matrix embedded with platelet boron nitride (p-BN) for thermal conduction and silicon-based compounds (S powder) for spectral selectivity. The p-BN flakes were aligned horizontally during the coating process to form structured thermal pathways, while the S powder was uniformly dispersed after KH560 modification to prevent aggregation. This configuration facilitated high in-plane thermal conductivity (1.73 W m⁻¹ K⁻¹), simultaneously realizing high reflectance in visible light and near-infrared band along with selective infrared emission at atmospheric window (ATW, 8–14 μm). The outdoor test showed that the emitter with 40 wt% p-BN reduced temperature by 2–4 ℃ below ambient. When subjected to a heat source, the emitter could also achieve a demonstrated cooling effect of 2–3 ℃ compared with the reference samples. Besides, the facile fabrication method of the emitter guaranteed the potential of mass production. This study featured selective absorbance, high internal thermal conductivity, facilitating practical applications and contributing to a comfortable indoor temperature.