Carrier Multiplication in Quantum Dots within the Framework of Two Competing Energy Relaxation Mechanisms

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• 作者：John T. Stewart ; Lazaro A. Padilha ; Wan Ki Bae ; Weon-Kyu Koh ; Jeffrey M. Pietryga ; Victor I. Klimov
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2013
• 出版时间：June 20, 2013
• 年：2013
• 卷：4
• 期：12
• 页码：2061-2068
• 全文大小：392K
• 年卷期：v.4,no.12(June 20, 2013)
• ISSN：1948-7185

文摘

The realization of high-yield, low-threshold carrier multiplication (CM) in semiconductor quantum dots (QDs) is a promising step toward third-generation photovoltaics (PV). Recent studies of QD solar cells have shown that CM can indeed produce greater-than-unity quantum efficiencies in photon-to-charge-carrier conversion, establishing the relevance of this process to practical PV technologies. While being appreciable, the reported CM yields are still not high enough for a significant increase in the power conversion efficiency over traditional bulk materials. At present, the design of nanomaterials with improved CM is hindered by a poor understanding of the mechanism underlying this process. Here, we present a possible solution to this problem by introducing a model that treats CM as a competition between impact-ionization-like scattering and non-CM energy losses. Importantly, it allows for evaluation of expected CM yields from fairly straightforward measurements of Auger recombination (inverse of CM) and near-band-edge carrier cooling. The validation of this model via a comparative CM study of PbTe, PbSe, and PbS QDs suggests that it indeed represents a predictive capability, which might help in the development of nanomaterials with improved CM performance.