Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395

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Author: search.filters.author.Sahin, MehmetPublisher: search.filters.publisher.Taylor & Francis Ltd

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  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    The Electronic and Optical Properties of a Triexciton in CdSe/ZnS Core/Shell Quantum Dot Nanocrystals
    (Taylor & Francis Ltd, 2016-02-21) Akturk, Abdurrahman; Tas, Hatice; Koksal, Koray; Sahin, Mehmet
    In the study, we aim to investigate the electronic and optical properties of single excitons, biexcions and triexcitons in a CdSe/ZnS core/shell quantum dot nanocrystal. The electronic structure has been determined by solving of the Poisson-Schrodinger equations self-consistently. In calculations, the exchange-correlation effects between identical particles have been taken into account in the frame of the local density approximation. We have demonstrated that the optical properties of triexciton systems are remarkably different from the single and biexciton systems. Absorption peaks or transition energies of the triexciton system are well separated from those of single- and bi-exciton systems. We have observed that the core-radius dependent transition energy variations of triexcitons are higher when compared with single- and bi-excitonic systems. The transition energy shifts of double and triple excitons with respect to the single exciton have been calculated as a function of the core radius and we have shown that the energy shifts are inversely proportional with the radius. We have also investigated the radius-dependent changes in binding energies and lifetimes of the structures and the comparative results have been discussed in a detail manner.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 3
    Effect of a Buffer Layer Between the Shell and Ligand on the Optical Properties of an Exciton and Biexciton in Type-II Quantum Dot Nanocrystals
    (Taylor & Francis Ltd, 2016-11-09) Koc, Fatih; Koksal, Koray; Sahin, Mehmet
    In this study, we have investigated the effect of the buffer layers on the electronic and optical properties of an exciton (X) and a biexciton (XX) in a type-II CdTe/CdSe quantum dot nanocrystal. In an experimental study, it has been reported that when a CdTe/CdSe quantum dot nanocrystal is coated by a ZnTe material as a buffer layer, the photoluminescence quantum yield is growing from 4 to 20%. We have confirmed theoretically this improvement and extended the calculations to an XX structure. In the calculations, two different semiconductor materials, CdS and ZnTe, have been considered for the buffer layer. We have theoretically shown that the buffer layer causes an increase in the radiative oscillator strength of both X and XX. When the ZnTe is used as the buffer layer, the oscillator strength becomes stronger when compared to CdSe buffer material because of higher conduction band offset between CdSe and ZnTe.