Abstract
Optical gain from colloidal quantum dots has been desired for several decades since their discovery. While gain from multiexcitations is by now well-established, nonradiative Auger recombination limits the lifetime of such population inversion in quantum dots. CdSe cores isovalently doped by one to few Te atoms capped with rod-shaped CdS are examined as a candidate system for enhanced stimulated emission properties. Emission depletion spectroscopy shows a behavior characteristic of 3-level gain systems in these quantum dots. This implies complete removal of the 2-fold degeneracy of the lowest energy electronic excitation due to the large repulsive exciton-exciton interaction in the doubly excited state. Using emission depletion measurements of the trap-associated emission from poorly passivated CdS quantum dots, we show that 3-level characteristics are typical of emission resulting from a band edge to trap state transition, but reveal subtle differences between the two systems. These results allow for unprecedented observation of long-lived population inversion from singly excited quantum dots.
Original language | English |
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Pages (from-to) | 817-824 |
Number of pages | 8 |
Journal | ACS nano |
Volume | 9 |
Issue number | 1 |
DOIs | |
Publication status | Published - Jan 27 2015 |
Keywords
- isovalent doping
- optical gain
- quantum dots
- stimulated emission
- trap emission
ASJC Scopus subject areas
- Materials Science(all)
- Engineering(all)
- Physics and Astronomy(all)