Observation of Size-Dependent Thermalization in CdSe Nanocrystals Using Time-Resolved Photoluminescence Spectroscopy

Hannah, Daniel C.; Dunn, Nicholas J.H.; Ithurria, Sandrine; Talapin, Dmitri V.; Chen, Lin X.; Pelton, Matthew; Schatz, George C.; Schaller, Richard D.

doi:10.1103/physrevlett.107.177403

Cited by 42 publications

(62 citation statements)

References 24 publications

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“…To account for the fact that the transient signal has negative and positive components, the absolute value of the change in scattering (|Δ S |) is used. These kinetics are well fit to a biexponential function with time components of 86 ± 24 ps—possibly due to NC cooling as it is on the order of CdSe NC cooling 46 —and a component of 510 ± 100 ps—which we attribute to the cubic-to-orthorhombic phase transition as it is on the same order as the amorphous-to-crystalline transition in CdSe NCs 37 , the most analogous process. There may also be faster features, which would require higher-time resolution instruments to resolve.…”

Section: Resultsmentioning

confidence: 78%

Photoinduced, reversible phase transitions in all-inorganic perovskite nanocrystals

et al. 2019

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Significant interest exists in lead trihalides that present the perovskite structure owing to their demonstrated potential in photovoltaic, lasing, and display applications. These materials are also notable for their unusual phase behavior often displaying easily accessible phase transitions. In this work, time-resolved X-ray diffraction, performed on perovskite cesium lead bromide nanocrystals, maps the lattice response to controlled excitation fluence. These nanocrystals undergo a reversible, photoinduced orthorhombic-to-cubic phase transition which is discernible at fluences greater than 0.34 mJ cm−2 through the loss of orthorhombic features and shifting of high-symmetry peaks. This transition recovers on the timescale of 510 ± 100 ps. A reversible crystalline-to-amorphous transition, observable through loss of Bragg diffraction intensity, occurs at higher fluences (greater than 2.5 mJ cm−2). These results demonstrate that light-driven phase transitions occur in perovskite materials, which will impact optoelectronic applications and enable the manipulation of non-equilibrium phase characteristics of the broad perovskite material class.

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Section: Resultsmentioning

confidence: 78%

Photoinduced, reversible phase transitions in all-inorganic perovskite nanocrystals

et al. 2019

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“…Colloidal quantum dots (CQDs) are specially attractive in this context since they can be prepared over a wide spectral range in highly monodisperse form and can also be easily assembled in to compact mono/multilayered films of arbitrary density using simple methods [6][7][8]. While the optical [9][10][11] and electro-optical properties [12][13][14][15] of these materials have been well studied, the necessity to push the limits of their quantum efficiencies (QE) for various applications has intensified research in this direction [16][17][18][19][20][21][22][23][24][25][26]. Some theoretical studies [27][28][29][30] in the recent past have suggested the possibility of obtaining the strong coupling and collective emission (CE) from an ensemble of quantum emitters like CQDs, mediated by plasmons.…”

Section: Introductionmentioning

confidence: 99%

Plasmon-mediated emergence of collective emission and enhanced quantum efficiency in quantum dot films

et al. 2015

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We present experimental and theoretical results on monolayer colloidal cadmium selenide quantum dot films embedded with tiny gold nanoparticles. By varying the density of the embedded gold nanoparticles, we were able to engineer a plasmon-mediated crossover from emission quenching to enhancement regime at interparticle distances for which only quenching of emission is expected. This crossover and a nonmonotonic variation of photoluminescence intensity and decay rate, in experiments, is explained in terms of a model for plasmonmediated collective emission of quantum emitters which points to the emergence of a new regime in plasmonexciton interactions. The presented methodology to achieve enhancement in optical quantum efficiency for optimal doping of gold nanoparticles in such ultrathin high-density quantum dot films can be beneficial for new-generation displays and photodetectors.

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“…1 However, this interface is difficult to access experimentally; at present the only estimates of interfacial thermal conductance for a SNC and its surroundings rely on fits to a modified effective medium theory 1 or lower-bound estimates based on characterization of thermal transport rates via optical spectroscopy. 2 Such measurements yield only averaged information regarding the thermal transport and the quality of available data is typically such that fits to effective medium theories yield estimates with 100% or greater uncertainties. 1 Theoretical modeling can provide microscopic insight into the underlying physics and guide the rational design of nanoscale materials with tailored thermal properties.…”

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confidence: 99%

Reverse Non-Equilibrium Molecular Dynamics Demonstrate That Surface Passivation Controls Thermal Transport at Semiconductor–Solvent Interfaces

et al. 2015

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We examine the role played by surface structure and passivation in thermal transport at semiconductor/organic interfaces. Such interfaces dominate thermal transport in semiconductor nanomaterials owing to material dimensions much smaller than the bulk phonon mean free path. Utilizing reverse nonequilibrium molecular dynamics simulations, we calculate the interfacial thermal conductance (G) between a hexane solvent and chemically passivated wurtzite CdSe surfaces. In particular, we examine the dependence of G on the CdSe slab thickness, the particular exposed crystal facet, and the extent of surface passivation. Our results indicate a nonmonotonic dependence of G on ligand-grafting density, with interfaces generally exhibiting higher thermal conductance for increasing surface coverage up to ∼0.08 ligands/Å(2) (75-100% of a monolayer, depending on the particular exposed facet) and decreasing for still higher coverages. By analyzing orientational ordering and solvent penetration into the ligand layer, we show that a balance of competing effects is responsible for this nonmonotonic dependence. Although the various unpassivated CdSe surfaces exhibit similar G values, the crystal structure of an exposed facet nevertheless plays an important role in determining the interfacial thermal conductance of passivated surfaces, as the density of binding sites on a surface determines the ligand-grafting densities that may ultimately be achieved. We demonstrate that surface passivation can increase G relative to a bare surface by roughly 1 order of magnitude and that, for a given extent of passivation, thermal conductance can vary by up to a factor of ∼2 between different surfaces, suggesting that appropriately tailored nanostructures may direct heat flow in an anisotropic fashion for interface-limited thermal transport.

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Observation of Size-Dependent Thermalization in CdSe Nanocrystals Using Time-Resolved Photoluminescence Spectroscopy

Cited by 42 publications

References 24 publications

Photoinduced, reversible phase transitions in all-inorganic perovskite nanocrystals

Photoinduced, reversible phase transitions in all-inorganic perovskite nanocrystals

Plasmon-mediated emergence of collective emission and enhanced quantum efficiency in quantum dot films

Reverse Non-Equilibrium Molecular Dynamics Demonstrate That Surface Passivation Controls Thermal Transport at Semiconductor–Solvent Interfaces

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