Multiple exciton generation
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Multiple exciton generation (MEG), or carrier multiplication, involves the generation of multiple electron-hole pairs from the absorption of a single photon. MEG may considerably increase the power conversion efficiency of nanocrystal based solar cells, though harvesting the energy maybe difficult because of the short lifetimes of the multiexcitons.
MEG has been demonstrated in synthesized nanocrystals (quantum dots) including PbS, PbSe, PbTe, CdS, CdSe, and InAs [1]. Recently, MEG has also been demonstrated in colloidal silicon nanocrystals [2].
The microscopic origin of MEG is still under debate and several possibilities have been suggested [3]:
- 1) Impact ionization.
- 2) Coherent superposition of single and multiexciton states.
- 3) Multiexciton formation through a virtual state.
[edit] References
- ^ MEG and electrical extraction from a PbSe quantum dot photoconductor. Applied Physics Letters 92, 031107 (2008)
- ^ MEG in colloidal silicon nanocrystals. Nano Letters 7, 2506 (2007)
- ^ Space-separated quantum cutting with silicon nanocrystals for photovoltaic applications. Nature Photonics 2, 105 (2008)
