Graphene and carbon black nano-composite polymer absorbers for a pyro-electric solar energy harvesting device based on LiNbO3 crystals

A novel scheme for solar energy harvesting based on the pyro-electric effect has been demonstrated. The proposed harvester is based on an optical system focusing solar radiation onto a ferroelectric crystal (i.e. lithium niobate). The face exposed to the heating source is coated with a nanocomposite material (i.e. carbon black and graphene particles) that greatly improves the adsorption of solar radiation. The solar energy focused onto the crystal through a simple optical system allows one to induce a thermal gradient able to generate electric charges. Experiments have been carried out indoor as well as outdoor (in Pozzuoli, Naples, Italy, on December). Results show that two configurations appear to be preferable: (a) pyro-electric element with carbon black-based coating and a Fresnel lens (surface of about 100cm2); (b) pyro-electric element with graphene-based coating and a Fresnel lens (surface of about 600cm2). In both experimental arrangements the maximum temperature variation reached locally onto the lithium niobate substrate is relatively high with peaks greater than 250°C. The maximum electrical power peak is of about 90μW and about 50μW for (a) and (b) respectively. The results of this first investigation are encouraging for further development of more efficient harvesting devices.