Research On Radiative Cooler Based On Optical Thin Film Structure

Radiative cooling refers to the behavior of objects or structures that transfer heat to icy outer space through strong absorption/radiation capabilities within the atmospheric transparency window(8-13?m)to achieve cooling.This paper focuses on the application of multilayer optical thin film devices in the field of radiative cooling,and proposes two types of multilayer optical thin film devices,radiative cooling modules and red,green and blue three-primary reflective radiative cooling filters.The work mainly involves the following contents:Firstly,the development,research results and detailed working principles of radiative cooling are introduced.In addition,this article also introduces the development history of optical films and the classification of color filters.Secondly,a simple and low-cost radiative cooler based on multilayer optical thin film is proposed in this work,which has an average emissivity of 96%within the atmospheric transparency window(8-13?m).The ultra-broadband emissivity property is realized by constructing the strongly overlapped optical resonances with a tandem structure composed of two lossy materials while an additional lossless material is adopted as the top layer to reduce the Fresnel reflection of the whole structure.The maximum cooling power density of the fabricated radiative cooler can reach 113.0W/m2 at night.When integrated with an excellent solar reflector that can reflect 97%incident solar power,it theoretically has the maximum cooling power of 83.0 W/m2 in the case of solar irradiance up to 1000 W/m2 at noon.Finally,based on the multilayer optical film structure,red-green-blue three-primary reflective radiative cooling color filters are proposed.On the contrary of the traditional reflective color filters that use absorbing material to absorb the transmitted light,the proposed radiative cooling color filters use single-sided polished substrates and reflect the transmitted light back to the original incident space in the form of diffuse with the help of the rough back surface.The average emissivity of the three-color cooling filters within the atmospheric transparency window is about 90%,and they have good angular insensitivity.The working temperatures of the proposed red,green and blue three-primary reflective radiative cooling color filters can be about 14.4?,19.4? and 16.3? lower than the traditional chemical dye color filters of the same color at the same intensity of solar radiation.