Carrier Multiplication and Its Reduction by Photodoping in Colloidal InAs Quantum Dots

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• 作者：J. J. H. Pijpers ; E. Hendry ; M. T. W. Milder ; R. Fanciulli ; J. Savolainen ; J. L. Herek ; D. Vanmaekelbergh ; S. Ruhman ; D. Mocatta ; D. Oron ; A. Aharoni ; U. Banin ; M. Bonn
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：March 22, 2007
• 年：2007
• 卷：111
• 期：11
• 页码：4146 - 4152
• 全文大小：200K
• 年卷期：v.111,no.11(March 22, 2007)
• ISSN：1932-7455

文摘

Carrier (exciton) multiplication in colloidal InAs/CdSe/ZnSe core-shell quantum dots (QDs) is investigatedusing terahertz time-domain spectroscopy, time-resolved transient absorption, and quasi-continuous waveexcitation spectroscopy. For excitation by high-energy photons (~2.7 times the band gap energy), highlyefficient carrier multiplication (CM) results in the appearance of multi-excitons, amounting to ~1.6 excitonsper absorbed photon. Multi-exciton recombination occurs within tens of picoseconds via Auger-type processes.Photodoping (i.e., photoinjection of an exciton) of the QDs prior to excitation results in a reduction of theCM efficiency to ~1.3. This exciton-induced reduction of CM efficiency can be explained by the twofolddegeneracy of the lowest conduction band energy level. We discuss the implications of our findings for thepotential application of InAs QDs as light absorbers in solar cells.