SBIR Phase I: Fabrication of low-bandgap nano-crystalline SiGeC thin films using the Plasma Enhanced Chemical Vapor Deposition (PECVD) technique

This Small Business Innovation Research (SBIR) Phase I project will develop nanocrystalline SiGeC thin films with an optical bandgap (Eg) in the range of 1.6-1.8 eV, and enhanced absorption characteristics, leading to low-cost, high-efficiency (>20%) photovoltaic devices. Previous attempts at improving the photovoltaic efficiency have not been consistent and successful. The proposed approach uses plasma-enhanced chemical vapor deposition (PECVD) technique to deposit these films, which allows greater control of the process by being able to manipulate the plasma and electron temperatures to control the ion density in the plasma, with an independent control of the process parameters. This flexibility does not exist in the currently used techniques. With the proposed technique, stable and consistent films of SiGeC can be deposited on the desired substrate at moderate temperatures. If successfully developed, this technique could provide higher efficiency solar cells for the alternative energy market. The goal of highly stable films, high deposition efficiency and process scalability for large-scale manufacturing can only be achieved if the basic process can be proven. The broader impacts of this research will be in the low-cost photovoltaic (PV) devices for power generation market. If successfully completed, this research could lead to a strong partnership between solar cell manufacturers and equipment manufacturers, leading to a potentially lucrative photovoltaics market. Currently, electricity generated with available PV devices is 3-4 times more expensive as the conventional electricity. The selected materials (Si, Ge and C) for the thin film are abundantly available, which can significantly reduce the raw materials costs. A large body of basic knowledge of the requirements of solar electricity for the competitive market already exists, which makes the development of the process with a realistic performance target easy to achieve. The main challenge for achieving this goal lies in being able to control the deposition process to assure a stable and robust process, as the previous work has not been able to achieve consistent results. The initial target of producing a triple-junction thin-film solar cell is a worthy first product demonstration, which will prove the efficacy of the proposed technique, and attract third-party funding with little difficulty.