The Effect of Temperature and Dot Size on the Spectral Properties of Colloidal InP/ZnS Core−Shell Quantum Dots

Narayanaswamy, Arun; Meijerink, Andries; Zaag, P. J. van der

doi:10.1021/nn9004507

Cited by 141 publications

(147 citation statements)

References 41 publications

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“…The increase in the linewidth of PL peaks with increasing temperature is typically ascribed to the increase in the homogeneous broadening, as a result of enhanced dephasing due to exciton-phonon scattering. 26,42,52 This model explains well the trend for the higher-energy band but is unable to account for the atypical behavior exhibited by the lowerenergy band.…”

Section: Temperature Dependence Of the Pl Spectra And Pl Decay In Thementioning

confidence: 94%

“…The spectral shift is essentially the same for both bands up to 250 K ͑ϳ70 meV redshift͒ but becomes dramatically different at higher T's: the lower-energy peak undergoes an even faster bathochromic shift ͑80 meV from 250 to 300 K͒ while the higher-energy band displays a 20 meV blueshift. Temperature-dependent spectral shifts are usually ascribed to the T dependence of the band gap, 15,26,52 which is nevertheless not yet well understood for semiconductor NCs. 52 Although the T dependence of the band gap of CdSe and CdTe QDs has not yet been studied in detail, it is clear that the redshifts observed here for the lower-energy peak are much larger ͑a factor 3-5͒ than those expected for CdTe or CdSe QDs of similar sizes.…”

Section: Temperature Dependence Of the Pl Spectra And Pl Decay In Thementioning

confidence: 99%

“…Temperature-dependent spectral shifts are usually ascribed to the T dependence of the band gap, 15,26,52 which is nevertheless not yet well understood for semiconductor NCs. 52 Although the T dependence of the band gap of CdSe and CdTe QDs has not yet been studied in detail, it is clear that the redshifts observed here for the lower-energy peak are much larger ͑a factor 3-5͒ than those expected for CdTe or CdSe QDs of similar sizes. 15 Moreover, the blueshift observed for the higher-energy peak upon increasing T above 250 K is unprecedented for CdTe or CdSe based NCs.…”

Section: Temperature Dependence Of the Pl Spectra And Pl Decay In Thementioning

confidence: 99%

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Formation of nanoscale spatially indirect excitons: Evolution of the type-II optical character of CdTe/CdSe heteronanocrystals

Donegá

2010

Phys. Rev. B

107

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In this work, the evolution of the optical properties of nanoscale spatially indirect excitons as a function of the size, shape, and composition of the heteronanostructure is investigated, using colloidal CdTe/CdSe heteronanocrystals ͑2.6 nm diameter CdTe core and increasing CdSe volume fraction͒ as a model system. Emphasis is given to quantitative aspects such as the absorption cross section of the lowest-energy exciton transition ͑ SS ͒, Stokes shift, linewidths, and the exciton radiative lifetime. The hole wave function remains confined to the CdTe core while the electron wave function is initially delocalized over the whole heteronanocrystal ͑type-I 1/2 regime͒, and gradually localizes in the CdSe segment as the growth proceeds, until the spatially indirect exciton transition becomes the lowest-energy transition ͑type-II regime͒. This results in a progressive shift of the optical transitions to lower energies, accompanied by a decrease in the oscillator strengths at emission energies and an increase in the exciton radiative lifetimes. The onset of the type-II regime is characterized by the loss of structure of the lowest-energy absorption band, accompanied by a simultaneous increase in the Stokes shift values and transition linewidths. This can be understood by considering the dispersion of the hole and electron states in k space. The SS values decrease rapidly in the type-I 1/2 regime but only slightly in the type-II regime. This shows that the indirect exciton formation leads primarily to redistribution of the oscillator strength of the lowest-energy transition over a wider frequency range. The total absorption cross section per ion-pair unit ͑i.e., integrated over all the exciton transitions͒ remains essentially constant during the heteronanocrystal growth, demonstrating that SS is redistributed from higher-energy transitions of both the CdTe and the CdSe segments, in response to the reduction in the electron-hole wavefunction overlap. Two radiative decay rates are observed and ascribed to exciton states with different degrees of localization of the electron wave function ͑an upper state with a faster decay rate and a lower state with a slower decay rate͒. The results presented here provide fundamental insights into nanoscale spatially indirect exciton transitions, highlighting the crucial role of a number of parameters ͑viz., electron-hole spatial correlation, exciton dispersion and exciton degeneracy, shape effects, and electronic coupling͒.

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Section: Temperature Dependence Of the Pl Spectra And Pl Decay In Thementioning

confidence: 94%

Section: Temperature Dependence Of the Pl Spectra And Pl Decay In Thementioning

confidence: 99%

Section: Temperature Dependence Of the Pl Spectra And Pl Decay In Thementioning

confidence: 99%

See 1 more Smart Citation

Formation of nanoscale spatially indirect excitons: Evolution of the type-II optical character of CdTe/CdSe heteronanocrystals

Donegá

2010

Phys. Rev. B

107

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“…Upon cooling to 10 K, the emission wavelength shifted to 632 nm reflecting increased bandgap while the FWHM decreased to 50 nm, as expected from eliminating phonon broadening. 10 A photoluminescence (PL) spectrum at an intermediate temperature of 140 K is shown in Figure 1.…”

mentioning

confidence: 99%

Temperature dependent recombination dynamics in InP/ZnS colloidal nanocrystals

et al. 2012

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“…All lab grade solvents including n-hexane, methanol, acetone, chloroform and ethanol were used as-received and without further purification. The synthesis process was adapted from previous reported literature 27,[31][32][33] . …”

Section: Methodsmentioning

confidence: 99%

The Effect of Fatty Amine Chain Length on Synthesis Process of Inp/Zns Quantum Dots

Ranjbar-Navazi¹,

Nemati²,

Akbarī³

et al. 2016

Orient. J. Chem

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Obtaining narrow size distribution through conventional methods used for quantum dots of group II-VI semiconductors is impractical in the case of III-V semiconductors specially InP/ZnS quantum dots because of molecular precursors depletion and growth stage continuation through Ostwald ripening process. Using fatty amines as activator along with precursors can lead to more monodispersed quantum dots. In this work, the effect of fatty amine chain length on InP/ZnS quantum dots synthesis was investigated. Octylamine, dodecylamine and oleylamine were used as the activator of InP/ZnS quantum dots synthesis. Synthesis progress and color changes in reaction mixture with time lapse, indicative of formed quantum dots concentration, was intensified in presence of fatty amines with shorter chain length. Quantum dots with smaller mean size and broader size distribution were synthesized in presence of longer fatty amines as a result of higher capping capacity of them. Thereupon the optical properties of quantum dots were affected by chain length of fatty amine. Longer wavelength of photoluminescence emission was achieved by using octylamine with the shortest chain length among selected fatty amines.

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The Effect of Temperature and Dot Size on the Spectral Properties of Colloidal InP/ZnS Core−Shell Quantum Dots

Cited by 141 publications

References 41 publications

Formation of nanoscale spatially indirect excitons: Evolution of the type-II optical character of CdTe/CdSe heteronanocrystals

Formation of nanoscale spatially indirect excitons: Evolution of the type-II optical character of CdTe/CdSe heteronanocrystals

Temperature dependent recombination dynamics in InP/ZnS colloidal nanocrystals

The Effect of Fatty Amine Chain Length on Synthesis Process of Inp/Zns Quantum Dots

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