Graphene/Semiconductor Schottky Junction Solar Cells

As one of the most effective way for solving the energy crisis and environmental pollution, photovoltaic power technology can potentially cope with people’s ever-growing electric power requirement with minimal deleterious environmental consequences. Considerable efforts have been explored in the past decades on silicon solar cell fabrication technologies. However, reducing the cost of solar cells during the process of increasing their efficiencies has become a big challenge. In order to reduce the cost of solar cell fabrication, a simple process at low temperature is necessary. Based on graphene/semiconductor Schottky junction solar cells, this thesis focuses on the investigation of photovoltaic performance of Gr/GaAs solar cell and further performance improvement. Moreover, photoelectric properties of r-GO film and performance of r-GO/Si Schottky junction solar cells have been investigated. The main conclusion includes:(1) By thermal treatment on back electrode of GaAs, design of back electrode structure and surface passivation of GaAs, the performance of CVD-Gr/GaAs solar cell can get increased after each step. After thermal treatment, the cell efficiency increased from 1.20% to 2.03%. With superior design of back electrode, the cell efficiency increased from 2.03% to 4.23%. Eventually, the cell efficiency can increase from 4.23% to 6.64% by surface passivation.(2) Performance enhancement of Gr/GaAs solar cell can be obtained by introducing a P3HT layer between graphene and GaAs, which is associated with the increased barrier height and reduced carrier recombination. By optimizing P3HT thickness, it is evident that much thin P3HT can not completely cover the surface of GaAs substrate so that a worse performance is shown.Once the thickness is too much thick, adsorption and recombination in P3HT become serious, resulting a worse performance. While the thickness of P3HT is 10 nm, the cell efficiency achieved 6.84%. In addition, after TFSA doping and employing TiO2 antireflective film, a quite high efficience of 13.7% was achieved, which is the highest efficiency as a new record for monolayer graphene/GaAs structured cells.(3) r-GO films with high performance are obtained via thermal reduction and successfully applied on a r-GO/Si Schottky junction solar cell. Photoelectric properties can be tuned by various reduction temperatures and film thicknesses.With the same thickness, r-GO film show higher reduction degree, conductivity and transparacy under high reduction temperature. Once reduced under the same reduction temperature, r-GO film shows the best photoelectric properties with a thickess of 28 nm. As for the r-GO/Si cell performance corresponding to these r-GO films,a highest efficiency of 3.36% was achieved for the 28 nm r-GO film, which is the record efficiency based on the r-GO film.All these conclusions above prove that the graphene/semiconductor Schottky junction solar cells possess great potential in application of low-cost and high efficiency solar cells.