Interface engineering for highly efficient graphene-on-silicon Schottky junction solar cells by introducing a hexagonal boron nitride interlayer

Graphene-on-silicon (Gr/Si) Schottky junction solar cells have recently attracted considerable interest as promising candidates for low-cost photovoltaic applications. However, the efficiency of Gr/Si cells is still much lower than that of crystalline Si solar cells, which is mainly attributed to the interface recombination of carriers due to the low Gr/Si Schottky barrier. Herein, a few-layer hexagonal boron nitride (h-BN) is introduced to engineer the Gr/Si interface for improving device performance. The h-BN can act as an effective electron-blocking/hole-transporting layer due to its unique properties and appropriate band alignment with Si, and thus the interface recombination was suppressed and the open circuit voltage was remarkably increased. On the other hand, the series resistance of solar cells decreases due to an improving conductivity of graphene on h-BN, leading to an increased short circuit current density. Furthermore, the interface defects and contamination arising from the layer-by-layer transfer process can be eliminated by using a directly grown Gr/h-BN heterostructure. As a result, a maximum efficiency of 10.93% was achieved by combining h-BN interlayer and co-doping of graphene with Au nanoparticles and HNO3, which shows the great potential of the novel Gr/h-BN/Si solar cells.