Toward Tandem Photovoltaic Devices Employing Nanoarray Graphene-Based Sheets

Graphene quantum dots (GQDs) are promising photonic materials for light harvesting. However, only low photoelectron conversion efficiency can be generated in single-junction graphene-based solar cells when isolated GQDs with the edge bonding defects are used as semiconductors. To address this issue, a four-junction GQD-based tandem solar cell with high theoretical conversion efficiency was proposed in this paper. Instead of isolated GQDs, nanoarray GQDs embedded in hexagonal host materials, such as graphane or boron nitride, was adopted as the photoactive layer. Utilizing our universal thermodynamic approach to the gap openings in low-dimensional graphene, nanoarray armchair-interfaced GQDs embedded in graphane to achieve the maximal diameter of confined GQDs are found preferential for fabricating tandem solar cell devices. Besides these, the separation between GQDs and the thickness of GQD-based sheets were determined. This contribution is of benefit to the application of graphene for solar cell devices.