Broadband solar irradiation reflection by multilayer photonic structures with randomized layer thickness

Reflecting components based on photonic crystals that are optimized to reflect the Sun irradiation are very useful for energy applications. The employment of photonic structures as back reflectors in solar cells is widely studied. Moreover, photo-thermal effect employing photonic crystals to enhance photocatalysis is recently attracting increasing attention. Here, we show the efficient reflectivity of the whole solar irradiation spectrum with multilayer disordered photonic structures. To build a multilayer photonic structure that reflects a wide portion of the solar irradiation, a structure with a random distribution of layer thicknesses has been designed. A sequence of thicknesses for a 30-layer photonic structure, which allows a remarkable reflectance in the infrared part of the solar irradiation, has been determined with a proper algorithm. The angular dependence of the reflection of the photonic structure has been also studied. Such multilayers are made with Earth abundant materials, i.e., silicon dioxide and zirconium dioxide.