“…Tetrapod-shaped nanocrystals (NCs) made of II-VI semiconductors have attracted a great deal of interest since the first report on their solution-processed chemical synthesis in 2000 [1]. Studies have been reported on tetrapods made of CdSe [1,20], CdS [20], CdTe [20,3,21,10,22,23,24,25,12], ZnTe [20], and their core-shell combinations (core-shell tetrapods denoted hereafter as csTPs) [4,26,27,28,11,16]. In addition to these synthesis and characterization studies, there have been reports on the application of tetrapods to photovoltaic cells [17,18,19] and single electron transistors [2].…”
The exciton states of strained CdTe/CdS core-shell tetrapod-shaped nanocrystals were theoretically investigated by the numerical diagonalization of a configuration interaction Hamiltonian based on the single-band effective mass approximation. We found that the inclusion of strain promotes the type-II nature by confining the electrons and holes in nonadjacent regions. This carrier separation is more efficient than that with type-II spherical nanocrystals. The strain leads to a small blue shift of the lowest exciton energy. Its magnitude is smaller than the red shift induced by increasing the shell thickness. Moreover, the larger arm diameter reduces the influence of both shell thickness and strain on the exciton energy. Considering the broken symmetry, a randomness induced carrier separation was revealed which is unique to a branched core-shell structure. The calculated shell thickness dependence of the emission energy agrees well with available experimental data.
“…Tetrapod-shaped nanocrystals (NCs) made of II-VI semiconductors have attracted a great deal of interest since the first report on their solution-processed chemical synthesis in 2000 [1]. Studies have been reported on tetrapods made of CdSe [1,20], CdS [20], CdTe [20,3,21,10,22,23,24,25,12], ZnTe [20], and their core-shell combinations (core-shell tetrapods denoted hereafter as csTPs) [4,26,27,28,11,16]. In addition to these synthesis and characterization studies, there have been reports on the application of tetrapods to photovoltaic cells [17,18,19] and single electron transistors [2].…”
The exciton states of strained CdTe/CdS core-shell tetrapod-shaped nanocrystals were theoretically investigated by the numerical diagonalization of a configuration interaction Hamiltonian based on the single-band effective mass approximation. We found that the inclusion of strain promotes the type-II nature by confining the electrons and holes in nonadjacent regions. This carrier separation is more efficient than that with type-II spherical nanocrystals. The strain leads to a small blue shift of the lowest exciton energy. Its magnitude is smaller than the red shift induced by increasing the shell thickness. Moreover, the larger arm diameter reduces the influence of both shell thickness and strain on the exciton energy. Considering the broken symmetry, a randomness induced carrier separation was revealed which is unique to a branched core-shell structure. The calculated shell thickness dependence of the emission energy agrees well with available experimental data.
“…Theoretical research into QDs usually assumes the simplification of spherical symmetry for the confinement potential, a geometry far different from the experimental studies in semiconductor QDs, but it makes possible the computation of excitonic contributions for the optical properties; recently, De Giorgi et al [19] found a way to produce spherical QDs using colloidal nanocrystals, thus demonstrating the possibility of their fabrication. However, the aim of the present paper is to perform a preliminary study of the behavior of heavy excitons under hydrostatic pressure embedded in spherical quantum dots; many of these features could be present in QDs of other shapes.…”
“…Only little is known about the ultrafast charge-carrier dynamics of nanocrystals with different shapes, that is, nanorods. − CdTe tetrapod-shaped nanocrystals (see Chart ) are quite complex, as they consist of four nanorodlike arms with wurtzite structure grown on a tetrahedron-shaped nanocrystal core . Only a few studies using optical spectroscopy were performed for this type of nanocrystal. ,, 1 …”
Section: Introductionmentioning
confidence: 99%
“…21 Only a few studies using optical spectroscopy were performed for this type of nanocrystal. 21,34,35 In this work we present femtosecond time-resolved transient absorption studies on CdTe tetrapod nanocrystals. The ultrafast bleach dynamics in the visible spectral range is discussed and compared to results on spherical nanocrystals and nanorods.…”
We present transient absorption studies with femtosecond time resolution on the electron-hole dynamics in CdTe tetrapod nanostructures. Electron-hole pairs are generated by optical excitation in the visible spectral range, and an immediate bleach and induced absorption signal are observed. The relaxation dynamics to the lowest excitonic state is completed in about 6 ps. Experiments with polarized excitation pulses give information about the localization of the excited-state wave functions. The influence of the nanocrystal shape on the optical properties of CdTe nanoparticles is discussed.
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