Multiexciton Dynamics in Infrared-Emitting Colloidal Nanostructures Probed by a Superconducting Nanowire Single-Photon Detector
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- 作者：Richard L. Sandberg ; Lazaro A. Padilha ; Muhammad M. Qazilbash ; Wan Ki Bae ; Richard D. Schaller ; Jeffrey M. Pietryga ; Martin J. Stevens ; Burm Baek ; Sae Woo Nam ; Victor I. Klimov
- 刊名：ACS Nano
- 出版年：2012
- 出版时间：November 27, 2012
- 年：2012
- 卷：6
- 期：11
- 页码：9532-9540
- 全文大小：601K
- 年卷期：v.6,no.11(November 27, 2012)
- ISSN：1936-086X
文摘
Carrier multiplication (CM) is the process in which absorption of a single photon produces multiple electron鈥揾ole pairs. Here, we evaluate the effect of particle shape on CM efficiency by conducting a comparative study of spherical nanocrystal quantum dots (NQDs) and elongated nanorods (NRs) of PbSe using a time-resolved technique that is based on photon counting in the infrared using a superconducting nanowire single-photon photodetector (SNSPD). Due to its high sensitivity and low noise levels, this technique allows for accurate determination of CM yields, even with the small excitation intensities required for quantitative measurements, and the fairly low emission quantum yields of elongated NR samples. Our measurements indicate an up to 60% increase in multiexciton yields in NRs versus NQDs, which is attributed primarily to a decrease in the electron鈥揾ole pair creation energy. These findings suggest that shape control is a promising approach for enhancing the CM process. Further, our work demonstrates the effectiveness of the SNSPD technique for the rapid screening of CM performance in infrared nanomaterials.