PHYS 54 |
| Semiconductor nanocrystals (NCs) are almost perfect emitters that combine size-controlled tunability of emission color with high photoluminescence quantum yields. Despite these favorable light-emitting properties, NCs are difficult to use in lasing. Because of exact balance between absorption and stimulated emission in NCs excited with single excitons, optical gain can only occur due to the NCs that contain at least two excitons. A resulting complication is fast optical-gain decay via nonradiative Auger recombination. Here, we demonstrate a practical approach for obtaining optical gain in the single-exciton regime, which eliminates the problem of ultrafast Auger decay. Specifically, we develop core/shell hetero-NCs that produce efficient spatial separations between electrons and holes. The resulting imbalance between positive and negative charges produces a strong local electric field, which breaks the exact balance between absorption and stimulated-emission in singly excited NCs and allows us to demonstrate optical amplification due to single excitons. |
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Nanostructured Materials
1:20 PM-5:20 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 338, Oral
Division of Physical Chemistry |