2 research outputs found
Mercury Telluride Colloidal Quantum Dots: Electronic Structure, Size-Dependent Spectra, and Photocurrent Detection up to 12 Ī¼m
HgTe colloidal quantum dots are synthesized with high monodispersivity with sizes up to ā¼15 nm corresponding to a room temperature absorption edge at ā¼5 Ī¼m. The shape is tetrahedral for larger sizes and up to five peaks are seen in the absorption spectra with a clear size dependence. The size range of the HgTe quantum dots is extended to ā¼20 nm using regrowth. The corresponding room temperature photoluminescence and absorption edge reach into the long-wave infrared, past 8 Ī¼m. Upon cooling to liquid nitrogen temperature, a photoconductive response is obtained in the long-wave infrared region up to 12 Ī¼m. Configuration-interaction tight-binding calculations successfully explain the spectra and the size dependence. The five optical features can be assigned to sets of single hole to single electron transitions whose strengths are strongly influenced by the multiband/multiorbital character of the quantum-dot electronic states
Size Dependence of the Exciton Transitions in Colloidal CdTe Quantum Dots
In this paper, we present a detailed investigation of
the size
dependence of the optical transitions of colloidal CdTe QDs ranging
in diameter from 2.9 to 14.8 nm. The energy integrated absorption
cross section per CdTe unit is investigated in detail for the lowest
two exciton transitions (1S<sub>3/2(h)</sub>ā1S<sub>(e)</sub> and 2S<sub>3/2(h)</sub>ā1S<sub>(e)</sub>) and shown to increase
with decreasing size, although the size dependence of the 2S<sub>3/2(h)</sub>ā1S<sub>(e)</sub> is less pronounced. The experimental absorption
spectra are compared to spectra calculated by using a tight-binding
approach. The calculations were carried out with electronāhole
configuration interaction (CI) and without (single-particle, SP).
The optical absorption spectra calculated by using the CI approach
are in excellent agreement with the experiment, as well as the evolution
of the optical gap and the optical transitions with nanocrystal size