Temperature Dependence of Förster Thermalization and Population Decay in PbSe Nanocrystals




Quintero-Torres, Rafael
van Veggel, Frank C.J.M.
Young, Jeff F.

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Journal of Physical Chemistry C


Time-resolved photoluminescence spectroscopy is used to quantify the Förster-mediated exciton migration rate and the exciton population decay rate in drop-cast solid emulsions of PbSe colloidal nanocrystals emitting near 1.5 μm from 77 to 300 K. For both unimodal and bimodal emulsions, at a fixed temperature in a given sample the measured time constants that characterize the fast transient decay (blue side of the spectrum) and buildup (red side of the spectrum) vary considerably with emission wavelength, but the average fast time constant, ∼25 ns, varies little (i.e., within <25%) with temperature from 77 to 300 K. Over the same temperature range, the exciton population lifetime, ascribed to nonradiative decay, decreases by ∼5 times but is always longer than the Förster time constant. The increase of the Förster-mediated efficacy of exciton redistribution at low temperatures before they decay is therefore almost all due to the variation of the nonradiative decay rate. By analyzing the temporally resolved and steady-state emission spectra, it is noted that the time required for the exciton population to equilibrate is nonexponential and considerably longer (∼150 ns) than the rapid decay and buildup time constants extracted from the decay curves at fixed wavelengths.



Nanocrystals, Optical properties, Exciton dynamics, Photoluminescence of semiconductors, Time resolved spectroscopy, Energy transfer between semiconductor nanocrystals


Quintero-Torres, R., van Veggel, F.C.J.M., & Young, J.F. (2014). Temperature Dependence of Förster Thermalization and Population Decay in PbSe Nanocrystals. Journal of Physical Chemistry C, 118(2), 1377-1385.