Provided is a radiation cooling substrate, sequentially composed of a broadband radiation absorption layer, a metal substrate, and a wavelength-selective infrared emission layer. Also provided is a method for preparing the aforementioned radiation cooling substrate, which simply involves placing the metal substrate into an electrophoresis tank and depositing the broadband radiation absorption layer and the wavelength-selective infrared emission layer on the two sides of the metal substrate, respectively. Additionally, a radiation cooling device is provided, comprising the above-mentioned radiation cooling substrate. |