Local-field effects on the spontaneous emission rate of CdTe and CdSe quantum dots in dielectric media

Abstract

The refractive index dependence of the spontaneous emission rate is determined using organically capped CdSe and CdTe quantum dots as probes. The radiative lifetime of the exciton emission is measured in a variety of apolar solvents with refractive indices n between 1.37 and 1.50. It is demonstrated that quantum dots provide a model system for testing theories on the influence of local-field effects on the spontaneous emission rate. The experimentally observed influence of n on the radiative lifetime is smaller than predicted by well-known models for local-field corrections but is in good agreement with a recently developed fully microscopic model for the local-field enhancement of the spontaneous emission rate.

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

“…This choice allows us to discuss the behavior of τ in realistic systems (typically n ranges [11] from 1.375 for hexane to 1.496 for toluene), without however losing generality. Indeed, it has recently been found experimentally [12] that the influence of the solvent refractive index on the PL lifetime of CdSe NQDs is small, consistently with the observed [13] insensitivity of the absorption cross section of CdSe NQDs on the solvent refractive index.…”

Coupled donors in quantum dots: Quantum size and dielectric mismatch effects

“…4͑d͒, where the modulus of the wave function ⌿͑r͒ restricted to the azimuthal angle = 0 is represented for both the ground and first excited states and three different values of the surroundings permittivity, i.e., out = 5.5 ͑absence of dielectric confinement͒, out = 3.9 ͑situation in which the homopolar character is recovered͒, and out =2 ͑a typical value of organic capping materials 30 ͒. The case shown in Fig.…”

“…[26][27][28] In addition to the well-known quantum size effect, the influence of the dielectric confinement ͑com-ing from the different dielectric response of the QD and the surrounding medium͒ on the donor levels has been revealed as a particularly noticeable effect in colloidal quantum dots as they are usually synthesized in media with a dielectric response rather different to that of the dot material. 26,29,30 Prompted by the important role of coupled impurities in nanotechnology, we present in this paper a theoretical study on the molecular properties of a D 2 + system confined in a spherical quantum dot. We focus on the influence of both the QD size and the dielectric mismatch on the radiative lifetime, the bonding-antibonding energy splitting, and the electron charge distributions in the lowest-lying D 2 + molecular states, and analyze the dependence of the results on the relative position of the donors inside the quantum dot.…”

Influence of Thiol Capping on the Exciton Luminescence and Decay Kinetics of CdTe and CdSe Quantum Dots

“…The lifetime is almost independent of the solvent and the functional group of the thiol and is close to the radiative lifetime of CdTe QDs. 21 Clearly, capping exchange with thiol molecules results in a reduced nonradiative decay, as is evidenced by the increase of the luminescence QE accompanied by a single-exponential decay of the emission. The higher luminescence efficiency is ascribed to a better surface passivation by the thiol capping molecules.…”