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January 22, 2008

GE breakthrough for cheap solar cells

GE Global Research, the centralized research organization of the General Electric Company (NYSE: GE), 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.




“GE’s demonstration of the silicon nanowire-based cell represents a significant breakthrough in our efforts to enable higher efficiency cells that can be produced at much lower production costs,” said Dr. Loucas Tsakalakos, Project Leader of GE’s Nano PV team. “Today, higher efficiency often comes with a higher price tag. Through the unique processing and materials property benefits enabled by nanotechnology, we’re aiming to break that paradigm and pave the way to making solar power more affordable for consumers while maintaining and even improving cell performance.”


Silicon nanowire solar cells by
L. Tsakalakos, J. Balch, J. Fronheiser, and B. A. Korevaar
General Electric-Global Research Center, Niskayuna, New York 12309, USA

O. Sulima and J. Rand
GE Energy-Solar Technologies, Newark, Delaware 19702, USA

Silicon nanowire-based solar cells on metal foil are described. The key benefits of such devices are discussed, followed by optical reflectance, current-voltage, and external quantum efficiency data for a cell design employing a thin amorphous silicon layer deposited on the nanowire array to form the p-n junction. A promising current density of ~1.6 mA/cm2 for 1.8 cm2 cells was obtained, and a broad external quantum efficiency was measured with a maximum value of ~12% at 690 nm. The optical reflectance of the silicon nanowire solar cells is reduced by one to two orders of magnitude compared to planar cells


Loucas Tsakalakos, Project Leader of GE’s Nano PV team, has a blog entry on this

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.


Hat tip to Al fin

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