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First-principles study of the influence of different interfaces and core types on the properties of CdSe/CdS core-shell nanocrystals
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. Indian Institute of Science, Bangalore-560 012, India.
2015 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, 10865Article in journal (Refereed) Published
Abstract [en]

With the expanding field of nanoengineering and the production of nanocrystals (NCs) with higher quality and tunable size, having reliable theoretical calculations to complement the experimental results is very important. Here we present such a study of CdSe/CdS core-shell NCs using density functional theory, where we focus on dependence of the properties of these NCs on core types and interfaces between the core and the shell, as well as on the core/shell ratio. We show that the density of states and the absorption indices depend rather weakly on the type of interface and core type. We demonstrate that the HOMO wavefunction is mainly localised in the core of the nanocrystal, depending primarily on the core/shell ratio. On the other hand the LUMO wavefunction spreads more into the shell of the nanocrystal, where its confinement in the core is almost the same in each of the studied structural models. Furthermore, we show that the radiative lifetimes decrease with increasing core sizes due to changes in the dipolar overlap integral of the HOMO and LUMO wavefunctions. In addition, the electron-hole Coulomb interaction energies follow a similar pattern as the localisation of the wavefunctions, with the smaller NCs having higher Coulomb interaction energies.

Place, publisher, year, edition, pages
2015. Vol. 5, 10865
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-248551DOI: 10.1038/srep10865ISI: 000355652900001OAI: oai:DiVA.org:uu-248551DiVA: diva2:799872
Available from: 2015-03-31 Created: 2015-03-31 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Theory and Modelling of Functional Materials
Open this publication in new window or tab >>Theory and Modelling of Functional Materials
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The diverse field of material research has been steadily expanding with a great help from computational physics, especially in the investigation of the fundamental properties of materials. This has driven the computational physics to become one of the main branches of physics, allowing for density functional theory (DFT) to develop as one of the cornerstones of material research. Nowdays, DFT is the method of choice in a great variety of studies, from fundamental properties, to materials modelling and searching for new materials. In this thesis, DFT is employed for the study of a small part of this vast pool of applications. Specifically, the microscopic characteristics of Zn1-xCdxS alloys are studied by looking into the evolution of the local structure. In addition, the way to model the growth of graphene on Fe(110) surface is discussed. The structural stability of silicon nanocrystals with various shapes is analysed in detail, as well.

DFT is further used in studying different properties of semiconductor nanocrystals. The size evolution of the character of the band gap in silicon nanocrystals is investigated in terms of changes in the character of the states around the band gap. The influence of various surface impurities on the band gap, as well as on the electronic and optical properties of silicon nanocrystals is further studied. In addition, the future use of silicon nanocrystals in photovoltaic devices is examined by studying the band alignment and the charge densities of silicon nanocrystals embedded in a silicon carbide matrix. Furthermore, the electronic and optical properties of different semiconductor nanocrystals is also investigated. In the case of the CdSe/CdS and CdS/ZnS core-shell nanocrystals the influence of the nanocrystal size and different structural models on their properties is analysed. For silicon nanocrystal capped with organic ligands, the changes in the optical properties and lifetimes is thoroughly examined with changes in the type of organic ligand.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 93 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1247
Keyword
nanocrystals, graphene, alloys, density functional theory, optical properties, electronic properties, core-shell structures, semiconductors
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-248513 (URN)978-91-554-9231-1 (ISBN)
Public defence
2015-05-27, Å10132 (Häggsalen), Ångström Laboratory, Lägerhydddsvägen 1, Uppsala, 13:30 (English)
Opponent
Supervisors
Available from: 2015-05-05 Created: 2015-03-30 Last updated: 2015-07-07

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