 When added to the top of a standard silicon solar cell, stacked arrays could significantly increase the efficiency of the silicon solar cell at a much lower cost per additional watt than that of the original cell itself because they could more efficiently absorb shorter wavelength light (i.e., higher-energy photons) than is possible in ordinary bulk silicon. |
Grown using the liquid phase deposition (LPD) process developed at Rice and exclusively licensed to Natcore, the array is comprised of silicon quantum dots with diameters of less than three nanometers. A nanometer is one billionth of a meter.
The ability to create a three dimensional matrix of quantum dots is a critical step toward the formation of a fully functioning tandem cell. This accomplishment assures that Natcore will have the ability to control independently both the wavelength region and the extent of the optical absorption in tandem cells as they are deposited on a standard silicon solar cell.
Independent control of these two factors gives Natcore complete flexibility to optimize the performance of the second junction in the case of a two-cell tandem device, or the additional two junctions in the case of a three-cell tandem device.
This situation is in stark contrast to the production of three-junction tandem solar cells for space application in which the device performance is deliberately compromised because of the lack of independent control over these two factors during cell fabrication. Tandem solar cells are a proven technology in space applications.
The major issue preventing their broad use in earth-based applications has been the need to use exotic semiconducting materials for the upper layers, and the expensive special vacuum processing technology that limits large-scale production. In contrast, Natcore's LPD technology eliminates the need for such materials and their costly processing.
When added to the top of a standard silicon solar cell, stacked arrays could significantly increase the efficiency of the silicon solar cell at a much lower cost per additional watt than that of the original cell itself because they could more efficiently absorb shorter wavelength light (i.e., higher-energy photons) than is possible in ordinary bulk silicon.
Theoretical calculations by independent research groups show that efficiency of over 30% for tandem solar cells in terrestrial sunlight is possible.
Chuck Provini, Natcore's president and CEO, notes "Efficiency of greater than 30% would represent approximately double the power output of today's commercial silicon solar cells, and would likely bridge the economic gap between solar and conventional power generation."
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