Effect of temperature on the spectral properties of InP/ZnS nanocrystals

Savchenko, S. S.; Вохминцев, А. С.; Weinstein, I. A.

doi:10.1088/1742-6596/961/1/012003

Cited by 11 publications

(7 citation statements)

References 17 publications

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“…CW VTPL data for the InP, InP/F, and InP/Cd NCs all show decreasing intensities with increasing temperature, consistent with the presence of thermally activated nonradiative decay in all three samples. Similar CW data have been reported elsewhere for unshelled InP NCs, and in fact, most VTPL studies have focused on time-averaged data of shelled InP NC samples, ,,,,,− but it is challenging to deduce any information about bright state population from such CW data. We conclude that the simple surface modifications described here can eliminate nonradiative recombination to a sufficient extent that these NCs behave photophysically similar to InP/ZnS and InP/ZnSe core/shell NCs with relatively thick passivating shells.…”

Section: Resultssupporting

confidence: 70%

“…The PLQY and the ratio of excitonic to trap PL intensities both increase across this series of samples. For all three samples, the excitonic PL shifts to lower energy and decreases in intensity with increasing temperature, as reported previously. ,− The PL intensities of all three samples also decrease with increasing temperature. Figure D–F shows excitonic PL decay dynamics measured as a function of temperature for the same series of NCs.…”

Section: Resultsmentioning

confidence: 83%

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Effects of Surface Chemistry on the Photophysics of Colloidal InP Nanocrystals

et al. 2019

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Indium phosphide (InP) semiconductor nanocrystals (NCs) provide a promising alternative to traditional heavy-metal-based luminescent materials for lighting and display technologies, and implementation of InP NCs in consumer products is rapidly increasing. As-synthesized InP NCs typically have very low photoluminescence quantum yields (PLQY), however. Although empirical methods have led to NCs with near-unity PLQYs, a fundamental understanding of how specific synthetic and post-synthetic protocols can alter the electronic landscape of InP NCs is still lacking. Here, we have studied a series of homologous InP NCs prepared from InP clusters using a combination of room-temperature and low-temperature time-resolved spectroscopies to elucidate how specific charge-carrier trapping processes are affected when various surface modifications are performed. The data allow identification of large PLQY increases that occur specifically through elimination of surface electron traps and provide a rationale for understanding the microscopic origins of this trap suppression in terms of elimination of undercoordinated surface In3+ ions. Despite essentially complete elimination of surface electron trapping when surface In3+ is addressed, hole trapping still exists. This hole trapping is shown to be partially suppressed by even very thin shell growth, attributable to elimination of undercoordinated surface phosphides. We also observe signatures of bright-dark excitonic splitting in InP NCs with only submonolayer surface coverage of select additives (divalent Lewis acids or fluoride anions)−signatures that have only been previously observed in thick-shelled InP NCs. Together, these synthetic and spectroscopic results improve our understanding of relationships between specific InP NC surface chemistries and the resulting NC photophysics.

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Section: Resultssupporting

confidence: 70%

Section: Resultsmentioning

confidence: 83%

Effects of Surface Chemistry on the Photophysics of Colloidal InP Nanocrystals

et al. 2019

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“…In this case, HG < Hvis and it corresponds to the half-width of the luminescence band of 250 meV for the QD-1 [22,25]. The same behavior is observed for the QD-2 exciton absorption band with HG = 370 ± 30 meV [23]. 8 -PL H(T) InP/ZnS [31].…”

Section: Half-width Of the Inp/zns Exciton Absorption Bandsupporting

confidence: 63%

“…Taking these contributions into account, we approximated the low-energy wing of the exciton band by a Gaussian function to quantitatively estimate H (see Figure 1b). The centers of the bands were set at energies E1 obtained using data from second-order derivative spectrophotometry [22,23]. The inset in Figure 1b shows the change in the optical density DG corresponding to the maximum of the approximating Gaussian.…”

Section: Half-width Of the Inp/zns Exciton Absorption Bandmentioning

confidence: 99%

“…During the investigations, a Janis CCS-100/204N closed-loop helium cryostat was used to vary the temperature. A detailed description of the experimental procedure and the results obtained are presented in [22,23]. Analysis of the behavior of the first exciton absorption band showed that its shift parameters correspond to the bulk and low-dimensional modifications of indium phosphide as the temperature decreases.…”

Section: Introductionmentioning

confidence: 99%

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Inhomogeneous Broadening of the Exciton Band in Optical Absorption Spectra of InP/ZnS Nanocrystals

Savchenko

Weinstein

2019

Nanomaterials

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In this work, we have simulated the processes of broadening the first exciton band in optical absorption spectra (OA) for InP/ZnS ensembles of colloidal quantum dots (QDs). A phenomenological model has been proposed that takes into account the effects of the exciton–phonon interaction, and allows one to analyze the influence of the static and dynamic types of atomic disorder on the temperature changes in the spectral characteristics in question. To vary the degree of static disorder in the model system, we have used a parameter δ, which characterizes the QD dispersion in size over the ensemble. We have also calculated the temperature shifts of the maxima and changes in the half-width for the exciton peaks in single nanocrystals (δ = 0), as well as for the integrated OA bands in the QD ensembles with different values of δ = 0.6–17%. The simulation results and the OA spectra data measured for InP/ZnS nanocrystals of 2.1 nm (δ = 11.1%) and 2.3 nm (δ = 17.3%), are in good mutual agreement in the temperature range of 6.5 K–RT. It has been shown that the contribution of static disorder to the observed inhomogeneous broadening of the OA bands for the QDs at room temperature exceeds 90%. The computational experiments performed indicate that the temperature shift of the maximum for the integrated OA band coincides with that for the exciton peak in a single nanocrystal. In this case, a reliable estimate of the parameters of the fundamental exciton–phonon interaction can be made. Simultaneously, the values of the specified parameters, calculated from the temperature broadening of the OA spectra, can be significantly different from the true ones due to the effects of static atomic disorder in real QD ensembles.

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