Controlling the Optical Properties of Inorganic Nanoparticles

Scholes, Gregory D.

doi:10.1002/adfm.200800151

Cited by 230 publications

(208 citation statements)

References 134 publications

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“…In recent years there have been exciting developments towards new NC materials, such as giant shells 64,65 , parabolic confinement potentials 66 and type II confinement potentials 63 . The ultimate photo-physical properties arising from this cornucopia of new materials are as yet to be investigated and provide a fertile ground for the future of cryogenic single NC spectroscopy.…”

Section: Exciton-trion Transitionsmentioning

confidence: 99%

Cryogenic Single-Nanocrystal Spectroscopy: Reading the Spectral Fingerprint of Individual CdSe Quantum Dots

Fernée

Tamarat

Lounis

2013

J. Phys. Chem. Lett.

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Spectroscopically resolved emission from single nanocrystals at cryogenic temperatures provides unique insight into physical processes that occur within these materials. At low temperatures, the emission spectra collapse to narrow lines, revealing a rich spectroscopic landscape and unexpected properties, completely hidden at the ensemble level. Since these techniques were first used, the technology of nanocrystal synthesis has matured significantly, and new materials with outstanding photostability have been reported. In this perspective, we show how cryogenic spectroscopy of single nanocrystals probes the fundamental excitonic structure of the band edge, revealing spectral fingerprints that are highly sensitive to a range of photophysical properties as well as nanocrystal morphology. In particular, spectral and temporal signatures of biexciton and trion emission are revealed, and their relevance to emerging technologies is discussed. Overall we show how cryogenic single nanocrystal spectroscopy can be used as a tool for understanding fundamental photophysics and guiding the synthesis of new nanocrystal materials.

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Section: Exciton-trion Transitionsmentioning

confidence: 99%

Cryogenic Single-Nanocrystal Spectroscopy: Reading the Spectral Fingerprint of Individual CdSe Quantum Dots

Fernée

Tamarat

Lounis

2013

J. Phys. Chem. Lett.

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“…In contrast, bulk PbSe has a small gap of 280 meV at 300 K 17 at the L point of the Brillouin zone, which makes it interesting for near-infrared optoelectronics applications. From a theoretical viewpoint, the fundamental properties of CdSe and CdTe NCs have been studied for several decades, [18][19][20][21][22][23] 18,24 ensuring transferability of the parameters for investigating the electronic structure of semiconductor nanostructures. 33 Presently used tight-binding parameters for PbSe are taken from Ref.…”

Section: B Square Superlatticesmentioning

confidence: 99%

Electronic structure of atomically coherent square semiconductor superlattices with dimensionality below two

et al. 2013

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The electronic structure of recently synthesized square superlattices with atomic coherence composed of PbSe, CdSe, or CdTe nanocrystals (NCs) attached along {100} facets is investigated using tight-binding calculations. In experimental realizations of these systems [W. H. Evers et al., Nano Lett. 13, 2317], NC facets are atomically bonded, resulting in single-crystalline sheets, which, due to their nanogeometry, have an effective dimensionality below two. We predict electronic structures composed of successive bands formed by strong coupling between the wave functions of nearest-neighbor NCs. This coupling is mainly determined by the number of atoms at the NC bonding plane. The band structures deviate markedly from that of the corresponding two-dimensional (2D) quantum well; the 2D case can be recovered, however, if the effects of the nanogeometry are gradually reduced. The width of the bands can reach hundreds of meV, ascribing highly promising transport properties to square superlattices. The band edges are located at k = 0 except for PbSe superlattices, where their position in k space surprisingly depends on the parity of the number of {100} atomic planes in the NCs. Our calculations demonstrate that semiconductors with dimensionality below two have a strong potential for (opto-)electronic, photovoltaic, and spintronic applications.

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“…9 For example, CdSe QDs demonstrate broad absorption and narrow (pure color) emission spectra, unmatched photostability, and bright luminescence (brightness) with high quantum yield. In addition, the color of their emission can be tuned in a wide range of the visible-light spectrum just by changing their size (see ref 10 for a recent review). However, the main roadblock for practical applications of these characteristics is the high sensitivity of QD optical properties to their surface passivation and chemical environment.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structure of Ligated CdSe Clusters: Dependence on DFT Methodology

et al. 2011

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Simulations of ligated semiconductor quantum dots (QDs) and their physical properties, such as morphologies, QDÀligand interactions, electronic structures, and optical transitions, are expected to be very sensitive to computational methodology. We utilize Density Functional Theory (DFT) and systematically study how the choice of density functional, atom-localized basis set, and a solvent affects the physical properties of the Cd 33 Se 33 cluster ligated with a trimethylphosphine oxide ligand. We have found that qualitative performance of all exchange-correlation (XC) functionals is relatively similar in predicting strong QDÀligand binding energy (∼1 eV). Additionally, all functionals predict shorter CdÀSe bond lengths on the QD surface than in its core, revealing the nature and degree of QD surface reconstruction. For proper modeling of geometries and QDÀligand interactions, however, augmentation of even a moderately sized basis set with polarization functions (e.g., LANL2DZ* and 6-31G*) is very important. A polar solvent has very significant implications for the ligand binding energy, decreasing it to 0.2À0.5 eV. However, the solvent model has a minor effect on the optoelectronic properties, resulting in persistent blue shifts up to ∼0.3 eV of the low-energy optical transitions. For obtaining reasonable energy gaps and optical transition energies, hybrid XC functionals augmented by a long-range HartreeÀFock orbital exchange have to be applied.

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Controlling the Optical Properties of Inorganic Nanoparticles

Cited by 230 publications

References 134 publications

Cryogenic Single-Nanocrystal Spectroscopy: Reading the Spectral Fingerprint of Individual CdSe Quantum Dots

Cryogenic Single-Nanocrystal Spectroscopy: Reading the Spectral Fingerprint of Individual CdSe Quantum Dots

Electronic structure of atomically coherent square semiconductor superlattices with dimensionality below two

Electronic Structure of Ligated CdSe Clusters: Dependence on DFT Methodology

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