Theoretical efficiency limit of graphene-semiconductor solar cells

The maximum power conversion efficiency (PCE) of graphene-semiconductor solar cells (GSSCs) is calculated with regard to the universal scaling laws of thermionic emission across graphene/3D-semiconductor Schottky junctions. The performance of GSSCs as a function of the interface Schottky barrier height and the bandgap of semiconductor (Eg) is investigated. Under ideal conditions, these photovoltaic cells reveal a broad maximum at E g = 1.1 – 1.7 eV with PCE exceeding 25%. The efficiency limits of graphene/silicon and graphene/GaAs solar cells are determined to be 25.5% and 27.5%, respectively. The effect of environmental temperature on the solar cell performance is also investigated, and it is found that to a good degree, the PCE of GSSCs varies linearly with temperature. The thermal coefficients of PCE for graphene/silicon and graphene/GaAs solar cells are obtained to be −0.076%/K and −0.058%/K, respectively. This study is of fundamental importance for GSSCs and provides insights for further improvements.