Colored Radiative Cooler Under Optical Tamm Resonance

Radiative cooling is a refrigeration technology which depends on the radiation characteristics of objects.It does not require any power input and reduces energy loss.Except for the conventional radiative cooler,the colored radiative cooler with decorative properties has attracted extensive attention of researchers.At present,high-performance colored radiative cooler mainly faces two challenges:on one hand,in order to obtain the colorful patterns,those colored radiative coolers sacrifice a large amount of cooling effect;on the other hand,the obtained colors are still relatively light or irregular with a strong dependence on the incident angle.In this paper,based on the design of the conventional radiative cooler,a colored radiative cooler under Tamm resonance is proposed to balance the conflict between the cooling effect and the color display,so as to achieve the angle-insensitive,high-purity color and better cooling performance.The main contents of this paper are as follows:First,we introduce the basic theory and design method of radiative cooling in detail.For the conventional radiative cooler,the basic formula and working principle of radiative cooling are derived from the theory of thermal radiation,heat convection and heat conduction in thermodynamics;For the colored radiative cooler,the working principle is obtained based on the color and radiative cooling theory.The genetic algorithm for structural design optimization and the transfer matrix method for optical simulation are introduced,which provide the theoretical research foundation for the subsequent researches.Second,according to the radiative cooling principle and genetic algorithm,the high-performance conventional radiative cooler is optimized.This cooler not only obtains near-ideal spectral characteristics,but also reduces the temperature by 9.69? when hc=6 W/m2/K.The effects of different placement angles,non-radiative heat coefficient and ambient temperature on the cooling performance are systematically studied to reduce the cost of device fabrication and the blindness of experimental testing.Third,combining color display and cooling function,a colored radiative cooler is proposed which consists of Tamm structure and emitter.Our results demonstrate that the cooling power densities of the radiative coolers with three subtractive primary colors at ambient temperature can reach about 44?52 W/m2,with their temperatures being reduced by 5?6 ? when hc=6 W/m2/K.Compared to the single emitter,only a steady-state temperature of?30%is sacrificed to enable the color displaying.Moreover,the color display and cooling performance of designed colored radiative cooler are insensitive of incident angle.The proposed design method and evaluation method of the colored radiative cooler can effectively guide the fabrication of the device.