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Träfflista för sökning "WFRF:(Sarma Dipankar Das) srt2:(2015)"

Sökning: WFRF:(Sarma Dipankar Das) > (2015)

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1.
  • Kocevski, Vancho, 1984-, et al. (författare)
  • First-principles study of the influence of different interfaces and core types on the properties of CdSe/CdS core-shell nanocrystals
  • 2015
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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2.
  • Lindblad, Rebecka, et al. (författare)
  • Electronic Structure of CH3NH3PbX3 Perovskites : Dependence on the Halide Moiety
  • 2015
  • Ingår i: The Journal of Physical Chemistry C. - American Chemical Society : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:4, s. 1818-1825
  • Tidskriftsartikel (refereegranskat)abstract
    • A combination of measurements using photoelectron spectroscopy and calculations using density functional theory (DFT) was applied to compare the detailed electronic structure of the organolead halide perovskites CH3NH3PbI3 and CH3NH3PbBr3. These perovskite materials are used to absorb light in mesoscopic and planar heterojunction solar cells. The Pb 4f core level is investigated to get insight into the chemistry of the two materials. Valence level measurments are also included showing a shift of the valence band edges where there is a higher binding energy of the edge for the CH3NH3PbBr3 perovskite. These changes are supported by the theoretical calculations which indicate that the differences in electronic structure are mainly caused by the nature of the halide ion rather than structural differences. The combination of photoelectron spectroscopy measurements and electronic structure calculations is essential to disentangle how the valence band edge in organolead halide perovskites is governed by the intrinsic difference in energy levels of the halide ions from the influence of chemical bonding.
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