The growing awareness of the energy situation and environmental concerns has motivated improving the efficiency of existing cooling systems and pursuing new alternative cooling technologies. Radiative cooling is an appealing concept for the 21st century in that its passive way to cooling and environmental sustainability. Fundamentally, radiative cooling is based on high solar reflection and infrared (IR) emission. For more efficient radiative cooling, selective IR emitters (SE) are necessary since most of the terrestrial thermal radiation at ambient temperature (i.e., 300K) can propagate through the atmospheric transparency spectral window (i.e., 8-13m) to ultra-cold heat sink (i.e., universe; 3K) . Research in recent decades has yielded a variety of passive selective emitter designs comprising sophisticated emissive coatings such as photonic structures, meta-materials, multi-stacking (>5 layers) structures. Although efficient, these designs are costly and demands complicated fabrication technology which can restrict the mass-production.