Radiative and Nonradiative Lifetime Engineering of Quantum Dots in Multiple Solvents by Surface Atom Stoichiometry and Ligands
by Omogo, Benard; Aldana, Jose F.; Heyes, Colin D.
CdTe quantum dots have unique characteristics that are promising for applications in photoluminescence, photovoltaics, or optoelectronics. However, wide variations of the reported quantum yields exist, and the influence of ligand surface interactions that are expected to control the excited state relaxation processes remains unknown. It is important to thoroughly understand the fundamental principles underlying these relaxation processes to tailor the QDs properties to their application. Here, we systematically investigate the roles of the surface atoms, ligand functional groups, and solvent on the radiative and nonradiative relaxation rates. Combining a systematic synthetic approach with X-ray photoelectron, quantitative FT-IR, and time-resolved visible spectroscopies, we find that CdTe QDs can be engineered with average radiative lifetimes ranging from nanoseconds up to microseconds. The nonradiative lifetimes are anticorrelated to the radiative lifetimes, although they show much less variation. The density, nature, and orientation of the ligand functional groups and the dielectric constant of the solvent play major roles in determining charge carrier trapping and excitonic relaxation pathways. These results are used to propose a coupled dependence between hole trapping on Te atoms and strong ligand coupling, primarily via Cd atoms, that can be used to engineer both the radiative and nonradiative lifetimes.
- Journal
- Journal of Physical Chemistry C
- Volume
- 117
- Issue
- 5
- Year
- 2013
- Start Page
- 2317-2327
- URL
- https://dx.doi.org/10.1021/jp309368q
- ISBN/ISSN
- 1932-7455; 1932-7447
- DOI
- 10.1021/jp309368q