Optical properties of alloyed CdSe/CdS CQDs heterostructure
Itay Meir a, Joanna Dehnel a, Efrat Lifshitz a
a Technion - Israel Institute of Technology, Haifa, Israel
Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe September Meeting 2017 (NFM17)
SE1: Fundamental Processes in Semiconductor Nanocrystals
Barcelona, Spain, 2017 September 4th - 9th
Organizers: Arjan Houtepen and Zeger Hens
Poster, Itay Meir, 060
Publication date: 20th June 2016

Colloidal semiconductor quantum dots (CQDs) are characterized by tunable electronic
properties with variation of size, shape and composition. Colloidal techniques facilitate
the formation of high-quality CQDs with surface passivation by molecular ligands,
hetero-structuring and scalable processing. Core/alloyed-shell CQDs characterized
by a smooth potential at the core-shell interface, thus permitting delocalization of
charge carriers toward the surface. Along with the development of the synthetic
procedures, numerous investigations have explored the optical and electrical
properties of these materials.
      This research investigates the influence of capping ligand or/and core/shell
heterostructure on the optical properties of the studied colloidal CQDs. The study used
cryogenic confocal microscope to detect the absorption spectra, photoluminescence
(PL), PL-lifetime, µ-PL and a polarization under a magnetic field of single dot. The
results supply information about the electronic states, their selective polarization
(reflecting on angular momentum) and recombination processes.
      The II-VI semiconductor CQDs comprised of core/shell structure are the
platform of the study. The results indicated blinking-free behavior. The examination
of the PL spectra pattern when excited with increase laser intensity, showed a merge
of the bands, more likely related to creation of multiple excitons. Moreover, following
the emission processes under the present of an external magnetic field and detection
via circular or/and linear polarizers indicated specific emission from selective bright
exciton and bi-exciton states. The influence of the ligands is examined when utilizing
a few different capping molecules, and the collection of the results is an on-going
process.
 

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