Summary
Development of silicon and III-V compound semiconductor nanostructures offers yet another path for low cost production and increased photovoltaic efficiencies. The real question is when how soon these advanced methods will become commercialized. The decisive factor for the success and production of solar modules is the manufacturing cost and how to drive cost lower while improving conversion efficiency.
Analysis
The Nano-Science Center at the University of Copenhagen has participated in the startup of four new nanotech companies – Dr. Aagesen’s company; Sunflake A/S is one of these. Sunflake appears to be in the development phase with the ultimate goal, according to their web site (www.sunflake.dk) to attain 30% conversion efficiency on low cost substrates capable of producing solar cells based on single crystal III-V nanostructures . The concept is to produce silicon nanostructures using MBE (molecular beam epitaxy) with their basic crystallographic planes oriented so as to be perpendicular to the plane of the substrate. Technology for forming nanostructures perpendicular to substrates is not new and has been described in prior work by Obraztsov, Pavlovsky and Volkov in 1998 for forming carbon nanoflakes (CNF). Work is also on going at Philips Research Laboratories for integrating III-V nanostructures to silicon for fabricating field effect transistors (FET) grown not by MBE but by laser ablation and MOVPE (metal-organic vapor-phase-epitaxy). While the Philips work is not directed toward solar applications it points to the need of “lattice matched substrates. Whereas the claim by Dr. Aagesen (SunFlake), is unique in that the n-p junctions required to form photovoltaic cells can be accomplished on “non-lattice matched substrates”. This could be a big cost advantage. The commercialization of Sunflake’s is probably a few years out and difficult to tell how successful it will be at this time. Nevertheless, and in Dr. Aagesen’s words, “…The potential is unmistakable…”
