Step-like enhancement of luminescence quantum yield of silicon nanocrystals

Publication Type:
Journal Article
Nature Nanotechnology, 2011, 6 (11), pp. 710 - 713
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Carrier multiplication by generation of two or more electron-hole pairs following the absorption of a single photon may lead to improved photovoltaic efficiencies1 and has been observed in nanocrystals made from a variety of semiconductors, including silicon. However, with few exceptions 2, these reports have been based on indirect ultrafast techniques3-6. Here, we present evidence of carrier multiplication in closely spaced silicon nanocrystals contained in a silicon dioxide matrix by measuring enhanced photoluminescence quantum yield. As the photon energy increases, the quantum yield is expected to remain constant, or to decrease as a result of new trapping and recombination channels being activated. Instead, we observe a step-like increase in quantum yield for larger photon energies that is characteristic of carrier multiplication7. Modelling suggests that carrier multiplication is occurring with high efficiency and close to the energy conservation limit. © 2011 Macmillan Publishers Limited. All rights reserved.
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