Directional and Spectral Control of Thermal Emission and Its Application in Radiative Cooling and Infrared Light Sources

The ability to control the directional and spectral properties of thermal emission is of fundamental importance for many applications. Here we propose a method to design directional and broadband thermal emitters (DBTEs) and directional and narrowband thermal emitters (DNTEs) based on classic thermal emitters and angular selectors. DBTEs exhibit strong thermal emission at a specific angle and within a broadband wavelength range. Besides, DBTEs achieve better radiative cooling performance than classic thermal emitters without special angular control when there are surrounding buildings. On the other hand, DNTEs can confine thermal emission within a narrow bandwidth and a narrow angular width. DNTEs show higher energy conversion efficiency than conventional narrowband thermal emitters, and have potential application in high-efficiency infrared light sources.