nn9b02834_si_001.pdf (1.28 MB)
Temperature-Induced Self-Compensating Defect Traps and Gain Thresholds in Colloidal Quantum Dots
journal contribution
posted on 2019-07-22, 18:44 authored by Randy
P. Sabatini, Golam Bappi, Kristopher T. Bicanic, Fengjia Fan, Sjoerd Hoogland, Makhsud I. Saidaminov, Laxmi K. Sagar, Oleksandr Voznyy, Edward H. SargentContinuous-wave
(CW) lasing was recently achieved in colloidal
quantum dots (CQDs) by lowering the threshold through the introduction
of biaxial strain. However, the CW laser threshold is still much higher
than the femtosecond threshold. This must be addressed before electrically
injected lasing can be realized. Here we investigate the relationship
between threshold and temperature and find a subpicosecond recombination
process that proceeds very efficiently at temperatures reached during
CW excitation. We combine density functional theory and molecular
dynamics simulations to explore potential candidates for such a process,
and find that crystal defects having thermally vibrating energy levels
can become electronic trapsi.e., they can
protrude into the bandgapwhen they are sufficiently distorted
at higher temperatures. We find that biaxially strained CQDs, which
have a lower femtosecond laser threshold than traditional CQDs, result
in less heat for a given transparency/gain level and thus undergo
this trapping to a lower extent. We also propose methods to tailor
CQDs to avoid self-compensating defect traps.
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Colloidal Quantum Dots Continuous-wavecrystal defectsself-compensating defect trapsbiaxial strainlasingCW laser thresholdGain Thresholdsfemtosecond laser thresholdsubpicosecond recombination processCQDfemtosecond thresholdquantum dotsenergy levelsdynamics simulationsTemperature-Induced Self-Compensating Defect TrapsCW excitation
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