Graphene-based derivative as interfacial layer in graphene/n-Si Schottky barrier solar cells

In Schottky barrier solar cell (SBSC), the interface between absorber and front electrode plays a vital role for reducing the dark current, blocking the majority carriers injected into the electrode at forward bias, reducing surface recombination and passivating the silicon surface. In this respect, the addition of interfacial layer between the semiconductor absorber and the metal electrode can reflect into an improvement of the device performance. Here we combine n-type crystalline silicon with stacks of graphene and graphene-based derivative (GBD) layers with different properties, in order to realize efficient SBSCs. Graphene layers with different structure, work function and electrical conductivity, were obtained by varying the chemical vapor deposition (CVD) parameters: conductive graphene films were grown at 1070 °C, GBD interfacial layers at 790 °C. The stacked structures were fabricated by the multiple transfer of these films. The films and the stacks were characterized by Raman spectroscopy. The device with the GBD interlayer (acting as hole transport layer) exhibits promising performances in terms of external quantum efficiency (EQE) and power conversion efficiency (PCE, ~5 %). Doping treatments with nitric acid vapor was performed and improved the cell PCE up to 6.7 %.