Charge Generation and Transport in CdSe Semiconductor Quantum Dot Solids

1999 ◽  
Vol 571 ◽  
Author(s):  
C. A. Leatherdale ◽  
N.Y. Morgan ◽  
C. R. Kagan ◽  
S. A. Empedocles ◽  
M. G. Bawendi ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Surface Passivation ◽  
Three Dimensional ◽  
Coulomb Energy ◽  
Charge Generation ◽  
Electron Hole ◽  
Initial Separation ◽  
Electron Hole Pair ◽  
Coulomb Glass ◽  
Current Transients

ABSTRACTWe demonstrate photoconductivity and conductivity in three-dimensional close-packed solids of colloidal CdSe quantum dots. We observe quantum dot size and surface passivation dependent photoconductivity that can be qualitatively understood by considering the energy required in order to overcome the Coulomb energy of the initial electron-hole pair. Our results suggest that surface ligands that promote initial separation of the electron and hole reduce the electric field required for the onset of the photocurrent. The dark conductance is much smaller than the photoconductance. Hysteretic behaviour and extremely long-lived current transients are observed in the dark current that are suggestive of Coulomb-glass behaviour.

A Hot Electron–Hole Pair Breaks the Symmetry of a Semiconductor Quantum Dot

Nano Letters ◽  
2013 ◽  
Vol 13 (12) ◽  
pp. 6091-6097 ◽  
Author(s):  
M. Tuan Trinh ◽  
Matthew Y. Sfeir ◽  
Joshua J. Choi ◽  
Jonathan S. Owen ◽  
Xiaoyang Zhu
Keyword(s):  
Quantum Dot ◽  
Hole Pair ◽  
Hot Electron ◽  
Electron Hole ◽  
Semiconductor Quantum Dot ◽  
Electron Hole Pair

scholarly journals Electronic structure of vertically coupled quantum dot-ring heterostructures under applied electromagnetic probes. A finite-element approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. E. Mora-Ramos ◽  
J. A. Vinasco ◽  
D. Laroze ◽  
A. Radu ◽  
R. L. Restrepo ◽  
...  
Keyword(s):  
Finite Element ◽  
Quantum Dot ◽  
Numerical Technique ◽  
Three Dimensional ◽  
Quantum Ring ◽  
Electric And Magnetic Fields ◽  
Electron Hole Pair ◽  
Electromagnetic Probes ◽  
Element Approach ◽  
Electron And Hole States

AbstractWe theoretically investigate the electron and hole states in a semiconductor quantum dot-quantum ring coupled structure, inspired by the recent experimental report by Elborg and collaborators (2017). The finite element method constitutes the numerical technique used to solve the three-dimensional effective mass equation within the parabolic band approximation, including the effects of externally applied electric and magnetic fields. Initially, the features of conduction electron states in the proposed system appear discussed in detail, under different geometrical configurations and values of the intensity of the aforementioned electromagnetic probes. In the second part, the properties of an electron-hole pair confined within the very kind of structure reported in the reference above are investigated via a model that tries to reproduce as close as possible the developed profile. In accordance, we report on the energies of confined electron and hole, affected by the influence of an external electric field, revealing the possibility of field-induced separate spatial localization, which may result in an indirect exciton configuration. In relation with this fact, we present a preliminary analysis of such phenomenon via the calculation of the Coulomb integral.

scholarly journals Photocreation of a dark electron-hole pair in a quantum dot

2020 ◽  
Vol 101 (16) ◽  
Author(s):  
Shiue-Yuan Shiau ◽  
Benoit Eble ◽  
Valia Voliotis ◽  
Monique Combescot
Keyword(s):  
Quantum Dot ◽  
Hole Pair ◽  
Electron Hole ◽  
Electron Hole Pair

Particle-Size Distribution of CdSe Quantum Dots Determined by Photoluminescence Spectroscopy

1989 ◽  
Vol 164 ◽  
Author(s):  
E.N. Prabhakar ◽  
C.A. Huber ◽  
D. Heiman
Keyword(s):  
Quantum Dots ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
State Energy ◽  
Energy Levels ◽  
Three Dimensional ◽  
Particle Diameter ◽  
Electron Hole ◽  
Electron Hole Pair

AbstractParticle-size distribution effects on the energy levels of semiconductor quantum dots are investigated. By examining the low temperature photoluminescence spectra of microcrystals of the binary semiconductor CdSe embedded in a glass matrix, the distribution of energy levels due to three-dimensional confinement is determined. Calculations of the electron-hole pair ground state energy provide a relation between confinement energy and particle diameter. This allows conversion of the photoluminescence lineshape directly into a distribution of particle radii and facilitates analysis of the observed properties of the material. With extension to other systems the technique can become a valuable tool in the study of semiconductor microparticle composites.

CHEMICAL POTENTIAL CALCULATION RELATIVE TO AN EXCITONIC GAS IN A NON-PARABOLIC QUANTUM DOT

2006 ◽  
Vol 20 (26) ◽  
pp. 1703-1706 ◽  
Author(s):  
M. A. GRADO-CAFFARO ◽  
M. GRADO-CAFFARO
Keyword(s):  
Quantum Dot ◽  
Fermi Energy ◽  
Chemical Potential ◽  
Energy Levels ◽  
Energy Calculation ◽  
Fermi Velocity ◽  
Fermi Energy Level ◽  
Electron Hole ◽  
Electron Hole Pair ◽  
Parabolic Quantum Dot

The Fermi energy level, that is, the chemical potential associated with an excitonic gas in a semiconductor within a non-parabolic quantum dot is calculated by determining previously the corresponding Fermi velocity of excitons conceived as confined in a spherical quantum box on the basis of the energy levels of the hydrogen atom. From the Fermi energy calculation, the reduced effective mass of an electron–hole pair is found to be dependent upon the spatial exciton density. In addition, some aspects related to quantization of the Fermi energy in question and temperature dependence are discussed.

scholarly journals Atomically thin photoanode of InSe/graphene heterostructure

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Haihong Zheng ◽  
Yizhen Lu ◽  
Kai-Hang Ye ◽  
Jinyuan Hu ◽  
Shuai Liu ◽  
...  
Keyword(s):  
High Efficiency ◽  
Three Dimensional ◽  
High Mobility ◽  
Anode Surface ◽  
Monolayer Graphene ◽  
Hydrogen Electrode ◽  
Electron Hole ◽  
Inse Crystal ◽  
Electron Hole Pair ◽  
Shed Light

AbstractAchieving high-efficiency photoelectrochemical water splitting requires a better understanding of ion kinetics, e.g., diffusion, adsorption and reactions, near the photoelectrode’s surface. However, with macroscopic three-dimensional electrodes, it is often difficult to disentangle the contributions of surface effects to the total photocurrent from that of various factors in the bulk. Here, we report a photoanode made from a InSe crystal monolayer that is encapsulated with monolayer graphene to ensure high stability. We choose InSe among other photoresponsive two-dimensional (2D) materials because of its unique properties of high mobility and strongly suppressing electron–hole pair recombination. Using the atomically thin electrodes, we obtained a photocurrent with a density >10 mA cm−2 at 1.23 V versus reversible hydrogen electrode, which is several orders of magnitude greater than other 2D photoelectrodes. In addition to the outstanding characteristics of InSe, we attribute the enhanced photocurrent to the strong coupling between the hydroxide ions and photo-generated holes near the anode surface. As a result, a persistent current even after illumination ceased was also observed due to the presence of ions trapped holes with suppressed electron-hole recombination. Our results provide atomically thin materials as a platform for investigating ion kinetics at the electrode surface and shed light on developing next-generation photoelectrodes with high efficiency.

Self-Induced Oscillation for Electron-Hole Pair Confined in Quantum Dot

2011 ◽  
Author(s):  
Tomoki Tagawa ◽  
Atsushi Tsubaki ◽  
Masamu Ishizuki ◽  
Kyozaburo Takeda ◽  
Jisoon Ihm ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Hole Pair ◽  
Electron Hole ◽  
Electron Hole Pair

EXCITON INSULATOR STATES IN MATERIALS WITH ‘MEXICAN HAT’ BAND STRUCTURE DISPERSION AND IN GRAPHENE

2015 ◽  
Vol 11 (1) ◽  
pp. 2927-2949
Author(s):  
Lyubov E. Lokot
Keyword(s):  
Band Structure ◽  
Three Dimensional ◽  
Dimensional Sphere ◽  
Electron Hole ◽  
Dinger Equation ◽  
Fermi Sphere ◽  
Zinc Blende ◽  
Bulk Gan ◽  
Structure Dispersion ◽  
Excitonic States

In the paper a theoretical study the both the quantized energies of excitonic states and their wave functions in grapheneand in materials with "Mexican hat" band structure dispersion as well as in zinc-blende GaN is presented. An integral twodimensionalSchrödinger equation of the electron-hole pairing for a particles with electron-hole symmetry of reflection isexactly solved. The solutions of Schrödinger equation in momentum space in studied materials by projection the twodimensionalspace of momentum on the three-dimensional sphere are found exactly. We analytically solve an integral twodimensionalSchrödinger equation of the electron-hole pairing for particles with electron-hole symmetry of reflection. Instudied materials the electron-hole pairing leads to the exciton insulator states. Quantized spectral series and lightabsorption rates of the excitonic states which distribute in valence cone are found exactly. If the electron and hole areseparated, their energy is higher than if they are paired. The particle-hole symmetry of Dirac equation of layered materialsallows perfect pairing between electron Fermi sphere and hole Fermi sphere in the valence cone and conduction cone andhence driving the Cooper instability. The solutions of Coulomb problem of electron-hole pair does not depend from a widthof band gap of graphene. It means the absolute compliance with the cyclic geometry of diagrams at justification of theequation of motion for a microscopic dipole of graphene where >1 s r . The absorption spectrums for the zinc-blendeGaN/(Al,Ga)N quantum well as well as for the zinc-blende bulk GaN are presented. Comparison with availableexperimental data shows good agreement.

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