Lifetime and polarization of the radiative decay of excitons, biexcitons, and trions in CdSe nanocrystal quantum dots

Abstract

Using the pseudopotential configuration-interaction method, we calculate the intrinsic lifetime and polarization of the radiative decay of single excitons (X), positive and negative trions (X + and X -), and biexcitons (XX) in CdSe nanocrystal quantum dots. We investigate the effects of the inclusion of increasingly more complex many-body treatments, starting from the single-particle approach and culminating with the configuration interaction scheme. Our configuration-interaction results for the size dependence of the single-exciton radiative lifetime at room temperature are in excellent agreement with recent experimental data. We also find that (i) whereas the polarization of the bright exciton emission is always perpendicular to the hexagonal c axis, the polarization of the dark exciton switches

Cryogenic Single-Nanocrystal Spectroscopy: Reading the Spectral Fingerprint of Individual CdSe Quantum Dots

“…However, in this case the trion state is only red-shifted by ~ 5 meV, far smaller than that of Fig 7a 30 and therefore is a signature of the oppositely charged trion. We note however that our previous assignments of the trion charge were tentative 26,30 as they relied on contradictory numerical calculations 54,55 and room temperature results using different materials 56 . We have recently resolved this contradiction using magneto-optical spectroscopy to unambiguously show that the negative trion has a small binding energy while the positive trion has a large binding energy 29 .…”

“…7a has a binding energy of approximately 17 meV. However, there are two possible trion charges, which are reported to have widely differing binding energies 54,55 . In materials with high biexciton efficiency, we expect that emission from both trion charges to be efficient.…”

Magneto-optical properties of trions in non-blinking charged nanocrystals reveal an acoustic phonon bottleneck

“…Stable trion emission has been reported at low temperatures, however, NCs exhibiting this emission were rare 24 . In addition, spectroscopic identification of the trion charge was tentative 19,24 , relying on conflicting numerical simulations 26,27 . In all cases, the reported trion emission was incidental.…”

Ultrafast Optical Spectroscopy Techniques Applied to Colloidal Nanocrystals

“…In the film instead, at high repetition rate and excitation level of 0.16 electron-hole pair injected per dot per pulse, the transient spectrum reveals a red-shifted emission with respect to the low-excitation spectrum; a weaker, blue-shifted component also appears. We attribute these two components respectively to negatively [56,57] and positively [58,59] charged nanocrystals.…”