Attractive versus repulsive excitonic interactions of colloidal quantum dots control blue-to red-shifting (and non-shifting) amplified spontaneous emission

Date
2013-11-21
Advisor
Instructor
Source Title
The Journal of Physical Chemistry Letters
Print ISSN
1948-7185
Electronic ISSN
Publisher
American Chemical Society
Volume
4
Issue
23
Pages
4146 - 4152
Language
English
Type
Article
Journal Title
Journal ISSN
Volume Title
Abstract

Tunable, high-performance, two-photon absorption (TPA)-based amplified spontaneous emission (ASE) from near-unity quantum efficiency colloidal quantum dots (CQDs) is reported. Besides the absolute spectral tuning of ASE, the relative spectral tuning of ASE peak with respect to spontaneous emission was shown through engineering excitonic interactions in quasi-type-II CdSe/CdS core/shell CQDs. With core shell size adjustments, it was revealed that Coulombic exciton-exciton interactions can be tuned to be attractive (type-I-like) or repulsive (type-II-like) leading to red- or blue-shifted ASE peak, respectively, and that nonshifting ASE can be achieved with the right core shell combinations. The possibility of obtaining ASE at a specific wavelength from both type-I-like and type-II-like CQDs was also demonstrated. The experimental observations were supported by parametric quantum-mechanical modeling, shedding light on the type-tunability. These excitonically engineered CQD-solids exhibited TPA-based ASE threshold as low as 6.5 mJ/cm(2) under 800 nm excitation, displaying one of the highest values of TPA cross-section of 44 660 GM.

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Book Title
Keywords
Inverted Core/shell Nanocrystals, Semiconductor Nanocrystals, Stimulated-emission, Light Amplification, Optical Gain, Wave-guides, Confinement, Energy, Dynamics, Regime
Citation
Published Version (Please cite this version)