Refractive index and extinction coefficient of hollow microspheres for solar reflection

While hollow microspheres and various porous structures have received much attention for solar reflection in the recent literature, their fundamental determinants of optical properties material selection criteria are relatively little known. Here, we study with varying refractive index extinction coefficient identify role determining reflectivity. Our simulations based on finite-difference time-domain method show effects between 1.5 100 10?6–100 wavelength region 0.2–2.4 ?m explain how reflectivity is attributed to a combination strong backscattering limited absorption. analysis indicates that ceramic materials high low such as Y2O3 promising. When randomly distributed diameter ranging from 0.5 1 ?m, our simulation shows reaches 0.97 even at 300 thickness, diffusion theory-based model predicts exceed 0.98 500 or 0.99 mm thickness. findings can guide optimal designs related toward complete enable breakthroughs thermal management deep-space applications.