Multiple exciton generation (MEG), or carrier multiplication, involves the generation of multiple electron-hole pairs from the absorption of a single photon. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena 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. In Physics and Engineering, energy transformation or energy conversion, is any process of transforming one form of Energy to another Fahlman B D has described a nanocrystal as any nanomaterial with at least one dimension ≤ 100nm and that is singlecrystalline A solar cell or photovoltaic cell is a device that converts Solar energy into Electricity by the photovoltaic effect. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός
MEG has been demonstrated in synthesized nanocrystals (quantum dots) including PbS, PbSe, PbTe, CdS, CdSe, and InAs [1]. A quantum dot is a Semiconductor whose Excitons are confined in all three Spatial dimensions. Lead(II sulfide (also spelled sulphide, see Sulfur#Spelling) is a Chemical compound, most often purified from the Mineral Galena Lead selenide () or lead(II selenide, a Selenide of Lead, is a Semiconductor material. Lead telluride is a compound of lead and Tellurium (PbTe it is a Narrow gap semiconductor. Cadmium sulfide is a chemical compound with the formula CdS. Cadmium sulfide is yellow in colour and is a semiconductor Cadmium selenide ( Cd[[Selenium Se]] is a solid binary compound of cadmium and selenium Indium arsenide, InAs, or indium monoarsenide, is a Semiconductor material, a Semiconductor composed of Indium and Arsenic 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. Microscopic is a term used to describe objects smaller than those that can easily be seen by the naked Eye and which require a lens or Microscope to see Impact ionization is the process in a material by which one energetic Charge carrier can lose energy by the creation of other charge carriers
- 2) Coherent superposition of single and multiexciton states.
- 3) Multiexciton formation through a virtual state.
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)
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