Strain in free standing CdSe/CdS core-shell nanorods

Rajadell, F.; Royo, Miquel; Planelles, Josep

doi:10.1063/1.3673256

Cited by 16 publications

(18 citation statements)

References 24 publications

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“…The large thickness of the CdS shell leads to a situation where the outer CdS monolayers are nearly undeformed. As a result, slightly different shell thickness within this size regime should have no significant influence on the strain 40 .…”

Section: Resultsmentioning

confidence: 99%

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Band structure engineering via piezoelectric fields in strained anisotropic CdSe/CdS nanocrystals

et al. 2015

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Strain in colloidal heteronanocrystals with non-centrosymmetric lattices presents a unique opportunity for controlling optoelectronic properties and adds a new degree of freedom to existing wavefunction engineering and doping paradigms. We synthesized wurtzite CdSe nanorods embedded in a thick CdS shell, hereby exploiting the large lattice mismatch between the two domains to generate a compressive strain of the CdSe core and a strong piezoelectric potential along its c-axis. Efficient charge separation results in an indirect ground-state transition with a lifetime of several microseconds, almost one order of magnitude longer than any other CdSe/CdS nanocrystal. Higher excited states recombine radiatively in the nanosecond time range, due to increasingly overlapping excited-state orbitals. k̇p calculations confirm the importance of the anisotropic shape and crystal structure in the buildup of the piezoelectric potential. Strain engineering thus presents an efficient approach to highly tunable single- and multiexciton interactions, driven by a dedicated core/shell nanocrystal design.

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Section: Resultsmentioning

confidence: 99%

“…Details on the underlying theory are given by Rajadell et al . 40 The strain-induced piezoelectric polarization, which is linearly related to strain, is calculated by . The determination of ɛ ij ( r ) is performed using the multiphysics mode of Comsol 4.2 software.…”

Section: Methodsmentioning

confidence: 99%

Band structure engineering via piezoelectric fields in strained anisotropic CdSe/CdS nanocrystals

et al. 2015

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“…This indicates that the oscillator strength is determined not only by the core and shell geometry, the synthesis details and associated CdSe/CdS interface propertiese.g. strain 43 or interface barriers 44 will lead to a further modification of f gap . Indeed, literature studies showing delocalization effects are usually performed on samples synthesized using the same seed, or even prepared taking aliquots from the same synthesis, to improve consistency within the sample set.…”

Section: Resultsmentioning

confidence: 99%

Band-edge oscillator strength of colloidal CdSe/CdS dot-in-rods: comparison of absorption and time-resolved fluorescence spectroscopy

et al. 2017

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We studied the oscillator strength f of the band gap transition in heteronanocrystals (hNCs) with a spherical CdSe core embedded in an elongated CdS shell. A comparison with f of core-only CdSe NCs confirmed a reduction of the electron-hole overlap in hNCs with a band gap larger than 2.05 eV or smaller than 1.98 eV. However, the decrease in f is limited to about 50% when compared to CdSe NCs, suggesting that residual confinement still localizes the electron near the core. We correlated f with the radiative lifetime obtained from multiexponential photoluminescence (PL) decay traces. The different components were attributed to radiative decay, or deep and shallow carrier trapping, respectively, using the PL quantum efficiency (QE) as a guideline. Our data highlight the challenges associated when extracting the radiative decay, and demonstrate the added value of absorption spectroscopy to obtain the band-edge oscillator strength and the associated radiative recombination rate in colloidal hNCs.

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“…28 The boundary conditions are zero normal stress for the free surface. 29 The strain tensor elements ǫ ij (r) is obtained using the multiphysics mode of Comsol 4.2 software. Exciton states are calculated following Ref., 26 but adding strain-induced potential terms.…”

Section: Methodsmentioning

confidence: 99%

Strain in Lattice-Mismatched CdSe-Based Core/Shell Nanoplatelets

2019

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We investigate the role of the stress arising between core and shell materials in colloidal CdSe/X hetero-nanoplatelets (X=ZnS,CdS,CdTe). The resulting strain distribution is calculated within the linear elastic regime, and its influence on the electronic structure with k•p theory. We show that strain shifts the energy of electrons and that of holes by several tens of meV. In structures with type-I band alignment the two shifts have opposite signs and the net effect on the exciton emission energy is small, but in type-II systems they add up. The strain response in colloidal NPLs is found to exhibit some differences as compared to that of epitaxial quantum wells, including sizable influence of lateral dimensions below 10 nm and potentially relevant effect of coupled strain-momentum terms of the Hamiltonian. We further show that asymmetric shell covering leads to bending of the nanoplatelet and tilted potential profiles along the strong confinement direction, analogous to a built-in electric field. We propose overcoating CdSe/CdS NPLs with an outer ZnS shell as a method to mitigate tunneling-induced redshift of emission via strain engineering.

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Strain in free standing CdSe/CdS core-shell nanorods

Cited by 16 publications

References 24 publications

Band structure engineering via piezoelectric fields in strained anisotropic CdSe/CdS nanocrystals

Band structure engineering via piezoelectric fields in strained anisotropic CdSe/CdS nanocrystals

Band-edge oscillator strength of colloidal CdSe/CdS dot-in-rods: comparison of absorption and time-resolved fluorescence spectroscopy

Strain in Lattice-Mismatched CdSe-Based Core/Shell Nanoplatelets

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