Resonant-reflecting/absorbing coatings for maximizing the efficiency of hybrid thermal-electric power generation

Solar energy is one of the fastest-rising forms of renewable energy, with photovoltaics (PV) being the most popular harvesting method. Photovoltaic solar cells suffer from limited exploitation of the solar spectrum, with unused light being the cause of parasitic phenomena such as thermalization and degradation of useful lifetime. These problems are overcome by hybrid thermal-electric power generation. In this scheme, a selective reflector-absorber provides the PV cell only with light that can be effectively converted into electrical energy and absorbs the rest of the solar spectrum, converting it to heat which is further utilized. This dramatically increases the useful lifetime of PV cells while increasing the overall energy conversion efficiency of the system. We present selective ultra-thin selective reflectors-absorbers, based on Fano-resonant optical coatings and metal-dielectric-metal optical coatings, which are tailored for typical single- and multi-junction solar cells. The tailored reflectance in the visible spectral region and absorption in the remainder of the ultraviolet and infrared solar spectrum enables up to 60.58 % total thermal-electric system efficiency.