Influence of an Al2O3 interlayer in a directly grown graphene-silicon Schottky junction solar cell

Graphene/Si Schottky junction solar cells are widely studied in relation to the harvesting of solar energy, but high efficiency is limited due to surface recombination at the interface. Moreover, surface defects, wrinkles, and impurities may arise during the wet transfer process of graphene. We propose an easy approach to fabricate high efficiency solar cells by using directly grown graphene on a textured substrate with a large active area. In our novel technique, we directly grow a few layers of graphene on top of Al2O3/Si by using plasma enhanced chemical vapor deposition. The high-k dielectric layer of Al2O3 acts as an electron blocking layer which minimizes the surface recombination at the interface. Furthermore, the barrier width is optimized by controlling the thickness of the Al2O3 interlayer to achieve the highest efficiency of 8.4%. The devices were not intentionally doped, and no aging effect was found in 9 months. We believe that our stable solar cell results indicate a new route for the production of metal-insulator-semiconductor Schottky junction solar cells with high efficiency without need of chemical doping of the emitter layer.