COLL 331 |
| Carrier multiplication (CM) is a process, in which absorption of a single photon produces not just one but multiple electron-hole pairs (excitons). CM is very efficient in quantum-confined semiconductor nanocrystals (NCs), whereas it is inefficient in bulk semiconductors. In bulk materials, CM is typically explained by impact ionization. Our recent studies indicate that in NCs, CM may be dominated by a different effect. Specifically, we analyze a novel physical mechanism for CM, in which biexcitons are generated from NC vacuum via the Coulomb interaction between two valence-band electrons. We also study various energy-loss processes that can compete with CM. One such process involves interactions with near-surface ligand molecules and/or matrix/solvent states. This energy relaxation channel is expected to be particularly efficient at high spectral energies because of the increased leakage of electronic wavefunctions outside the NC and the possibility of direct exchange coupling of the NC states to ligand/matrix states. |
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Interfacial Electron Transfer and Solar Energy Conversion: From Molecules to Nanomaterials
2:00 PM-5:40 PM, Tuesday, April 8, 2008 Morial Convention Center -- Rm. 226, Oral
Division of Colloid & Surface Chemistry |