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Technology Stocks : Energy Conversion Devices

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To: alfranco who wrote (7682)	5/13/2004 3:21:43 AM
From: alfranco	Read Replies (3) of 8393

Del, here's the Los Alamos paper: arxiv.org They say that with PbSe nanocrystal material, they can get 2 and sometimes even 3 excitons when the pump photon energies are more than 3 times the nanocrystal's band gap energy. They also mention that the theoretical limit of solar cell conversion efficiency, requiring photon energies 3x the semiconductor's band gap, would yield a calculated 10% increase in efficiency and if this effect could be generated at a lower threshold of only 2x the semiconductor's band gap, this would yield a calculated 37% increase in efficiency. Again they are using high bandgap photons (ultraviolet) for 3x band gap (3.10eV) for PbSe and they state PbSe has a tunable band gap from 1.3eV down to .3eV. Microcrystalline Si, which we've worked with, has bandgap of 1.1eV but I don't even know if a 2nd electron in Si can be moved from the valence band to the conduction band to form via 'impact ionization' a biexciton as the researchers have found with PbSe. I'm just guessing there is something inherent in the electron orbitals of this PbSe material that makes its' electrons much jumpier ;-) Al

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