The role of oxygen defects engineering via passivation of the Al2O3 interfacial layer for the direct growth of a graphene-silicon Schottky junction solar cell

Abstract

Over the past decade, graphene-based solar cells have received increasing exploration. In particular, the metal–insulator–semiconductor (MIS)-type solar cells have an inherent cost advantage compared to the p-n junction solar cells. However, the technological progress in graphene solar cells based on the MIS junction is currently facing a number of serious challenges, including long-term stability, surface recombination at the interface level, and surface defects. To overcome these barriers, a simple, cost-effective method is developed herein for the interfacial single-component passivation of Al2O3 with NH3 or H2O2, and co-passivation with NH3 and H2O2 together. The interfacial layer between the silicon and the directly-grown graphene operates as an effective electron blocking layer, thus leading to the minimization of surface recombination. Further, the NH3-H2O2 co-passivated Al2O3 performs the dual role of providing a good platform for the growth of graphene and enhancing the performance of the fabricated solar cell. Moreover, in a proof of concept demonstration, the fabricated graphene-silicon (Gr/Si) Schottky junction with an NH3-H2O2 co-passivated Al2O3 interfacial layer exhibits an efficiency of 9.49%, which is a major enhancement over that of the Gr/Si solar cell without an interfacial layer (i.e., 3.19%). These results demonstrate that the control of oxygen-related defects containing non-lattice oxygen in the Al2O3 interfacial layer remarkably impacts the charge transfer resistance and electron recombination processes. This work can be viewed as an elegant interface engineering approach to the co-passivation of Al2O3 for optoelectronic applications.