General Electric Silicon Nano-Wire PV
GE Global Research, the centralized research organization of the General Electric Company, announced that scientists on their Nano Photovoltaics (PV) team have demonstrated a scalable silicon nanowire-based solar cell, which has the potential to achieve up to 18% efficiency and be produced at a dramatically lower cost than conventional solar cells. This demonstration represents a promising development in the effort to make PV systems more economically viable for consumers.Given General Electric's prominent position in the conventional power industry, its substantial investment in renewable energies should cause many investors and venture capitalists to pay even more attention than previously.
GE reported its development recently in the journal Applied Physics Letters, which can be accessed online. The paper also was featured in the Virtual Journal of Nanoscale Science and Technology, which highlights the latest research in nanotechnology from various science journals. NextEnergy
The cells were fabricated on a metal foil substrate, thus showing potential for future roll-to-roll manufacturing of such devices. We used standard, scaleable processes to grow the nanowires and to fabricate p-n junctions conformally around the nanowires. The use of conformal p-n junctions allows for de-coupling light absorption from charge transport. In a standard solar cell the active material must be thick enough to absorb all the sunlight (for silicon this is > 125 micrometers), however, as charge carriers diffuse back to the p-n junction many are lost due to non-radiative recombination. In these nanowire-based devices the minority carriers must only diffuse a few hundred nanometers to reach the charge-separating junction. The nanowire cells also showed the expected improvements in their optical properties. While the power conversion efficiency in these devices is still low, and much work remains to improve the performance, this nanoscale solar cell architecture and processing approach has promise to create a new paradigm in solar cell manufacturing and device design in the future. SourceGE has an ongoing collaboration with the U.S. Department of Energy (DOE) and is managing a three-year, $46.7 million project that is looking across the entire value chain to make solar energy more cost effective and more readily available in the marketplace. The program is evaluating three different technologies for the solar cell: high efficiency silicon-based cells, molded silicon wafers, and flexible thin films. DOE’s Solar America Initiative is designed to make solar energy cost-competitive with conventional forms of electricity by 2015. Of its own accord, GE has committed to more than doubling its level of investment in environmentally friendly technologies like solar from $700 million to $1.5 billion by the year 2010. GE is well on track to meet its commitment, surpassing the $1 billion mark in R+D spending this year.Gizmag
Other companies involved in nanowire PV include Cleanfield Alternative Energy Inc.
Brian Wang discusses more nanowire PV projects here.