A highly robust and stable graphene-encapsulated Cu-grid hybrid transparent electrode demonstrating superior performance in organic solar cells

Copper is one of the candidate materials for alternative transparent conductive electrodes (TCEs) owing to its excellent electrical conductivity and low cost. The vulnerability of copper against oxidation, however, imposes a severe limitation on its widespread application in functional devices. In this study, we demonstrate a high-performance and robust Cu and graphene hybrid TCE, where Cu optimized in a grid structure was used as the base electrode, while graphene sheet provided additional charge collection and transport pathways as well as a protective layer against oxidation of the underlying Cu. The Cu grid/graphene hybrid TCE was demonstrated in organic solar cells (OSCs) to have a power conversion efficiency of 8.5%, which is among the best performances based on metal grid TCE-based OSCs. The resulting device exhibited excellent long-term and thermal stabilities as well. The proposed Cu grid/graphene hybrid structure is expected to find practical application in various optoelectronics devices.