On the use of graphene to improve the performance of concentrator III‐V multijunction solar cells

Abstract Graphene has been intensively studied in photovoltaics focusing on emerging solar cells based on thin films, dye‐sensitized solar cells, quantum dots, nanowires, and so forth. However, the typical efficiency of these solar cells incorporating graphene is below 16%. Therefore, the photovoltaic potential of graphene has not yet been shown. In this work, the use of graphene for concentration applications on III‐V multijunction solar cells, which indeed are the solar cells with the highest efficiency, is demonstrated. First, a wide optoelectronic characterization of graphene layers is carried out. Then, the graphene layer is incorporated onto triple‐junction solar cells, which decreases their series resistance by 35% (relative), leading to an increase in fill factor of 4% (absolute) at concentrations of 1000 suns. Simultaneously, the optical absorption of graphene produces a relative short‐circuit current density decrease in the range of 0% to 1.8%. As a result, an absolute efficiency improvement close to 1% at concentrations of 1000 suns was achieved with respect to triple‐junction solar cells without graphene. The impact of incorporating one and two graphene monolayers is also evaluated.