Efficiency of Photovoltaic Cells—A Comparison between Silicon and Graphene ^†

Photovoltaic cells are electronic devices built using solid-state semiconductors. Its working principle is based on the photovoltaic effect, which consists of the production of electrical energy whenever a given material receives the incidence of photons or light radiation from the Sun or another light source, with a certain wavelength. Currently, one of the most used semiconductor materials for the manufacture of photovoltaic cells is Silicon, which, through the doping technique, interacts with other elements (such as Boron or Phosphorus) to form a potential difference, as a result of the application of an external electric field, giving rise to electrical energy. Silicon-based photovoltaic cells have an energy conversion efficiency of light radiation into electrical energy in the order of 18%. However, a recently discovered material that can be used to build high-efficiency photovoltaic cells is graphene. Graphene is a material that arises from graphite, with a two-dimensional structure, and one atom thick. It is made up of hexagonally linked carbon atoms. This material has excellent electrical and optical characteristics, which can be very useful for making photovoltaic cells, due to the fact that the electrons in graphene have high mobility, having the behavior of massless particles, such as Dirac fermions. Recent experiments carried out at the level of the international scientific community reveal that photovoltaic cells based on graphene can achieve energy conversion efficiency above 20%, and that a combination of solar cells made of silicon and graphene can achieve efficiencies above 30%. As a result of a bibliographic research, the present work seeks to present a comparative picture between photovoltaic cells made of silicon and those built on graphene.