Terahertz-Driven Luminescence and Colossal Stark Effect in CdSe–CdS Colloidal Quantum Dots
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acs.nanolett.7b01837.pdf
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Author(s)
Zhao, Xiaoguang
Zhang, Xin
Pein, Brandt C
Chang, Wendi
Scherer, Jennifer Marie
Coropceanu, Igor
Bulovic, Vladimir
Bawendi, Moungi G
Nelson, Keith Adam
Date Issued
September 2017
Journal
Nano Letters
Publisher
American Chemical Society (ACS)
Citation
Pein, Brandt C. et al. “Terahertz-Driven Luminescence and Colossal Stark Effect in CdSe–CdS Colloidal Quantum Dots.” Nano Letters 17, 9 (August 23, 2017): 5375–5380 © 2017 American Chemical Society
Version
Final published version
Abstract
Optical properties of colloidal semiconductor quantum dots (QDs), arising from quantum mechanical confinement of charge, present a versatile testbed for the study of how high electric fields affect the electronic structure of nanostructured solids. Studies of quasi-DC electric field modulation of QD properties have been limited by electrostatic breakdown processes under high externally applied electric fields, which have restricted the range of modulation of QD properties. In contrast, here we drive CdSe-CdS core-shell QD films with high-field THz-frequency electromagnetic pulses whose duration is only a few picoseconds. Surprisingly, in response to the THz excitation, we observe QD luminescence even in the absence of an external charge source. Our experiments show that QD luminescence is associated with a remarkably high and rapid modulation of the QD bandgap, which changes by more than 0.5 eV (corresponding to 25% of the unperturbed bandgap energy). We show that these colossal energy shifts can be explained by the quantum confined Stark effect even though we are far outside the regime of small field-induced shifts in electronic energy levels. Our results demonstrate a route to extreme modulation of material properties and to a compact, high-bandwidth THz detector that operates at room temperature.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
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DOI of Published Version
https://doi.org/10.1021/acs.nanolett.7b01837
