Related Experiment Video
Updated: Jun 2, 2026

14:58
Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping
Published on: June 3, 2015
Wave function engineering for ultrafast charge separation and slow charge recombination in type II core/shell quantum
Haiming Zhu1, Nianhui Song, Tianquan Lian
1Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
Journal of the American Chemical Society
|May 4, 2011
Summary
Type II core/shell quantum dots (QDs) like CdTe/CdSe exhibit ultrafast charge separation and slow recombination. This makes these semiconductor quantum dots ideal for efficient solar energy conversion applications.
Area of Science:
- Materials Science
- Nanotechnology
- Photochemistry
Background:
- Semiconductor quantum dots (QDs) exhibit size-dependent optical and electronic properties.
- Core/shell QDs offer tunable properties by controlling electron and hole wave function localization.
- Type II core/shell QDs, like CdTe/CdSe, spatially separate electrons and holes.
Purpose of the Study:
- To investigate the charge transfer dynamics in type II CdTe/CdSe-anthraquinone (AQ) complexes.
- To evaluate the potential of type II QDs for solar energy conversion.
Main Methods:
- Ultrafast transient absorption spectroscopy.
- Fabrication of CdTe/CdSe core/shell quantum dots.
- Adsorption of anthraquinone (AQ) as an electron acceptor.
Main Results:
- Observed ultrafast intra-QD electron transfer (~770 fs) from CdTe core to CdSe shell.
- Demonstrated electron transfer from shell to adsorbed AQ (2.7 ps half-life).
- Showed significantly retarded charge recombination (92 ns half-life) compared to CdSe-AQ complexes.
Conclusions:
- Type II CdTe/CdSe QDs facilitate ultrafast charge separation and slow recombination.
- This property enhances efficiency for light-harvesting applications.
- Type II QDs are promising materials for advanced solar energy conversion.
Related Concept Videos
Energy Associated With a Charge Distribution
The work done to bring a charge through a distance r is given by the potential difference between the initial and the final position. To assemble a collection of point charges, the total work done can be expressed in terms of the product of each pair of charges divided by their separation distance, defined with respect to a suitable origin. Solving this expression gives the energy stored in a point charge distribution.
Continuous Charge Distributions
Imagine a bucket of water. It contains many molecules, of the order of 1026 molecules. Thus, although it contains discrete elements (molecules) at the microscopic level, macroscopically, it can be considered continuous. Small volume elements of water, infinitesimal compared to the bulk of the bucket's volume, still contain many molecules. Under this framework, quantized matter is approximated as continuous for practical purposes.
The electric charge can also be subjected to an analogical...
The electric charge can also be subjected to an analogical...
The de Broglie Wavelength
In the macroscopic world, objects that are large enough to be seen by the naked eye follow the rules of classical physics. A billiard ball moving on a table will behave like a particle; it will continue traveling in a straight line unless it collides with another ball, or it is acted on by some other force, such as friction. The ball has a well-defined position and velocity or well-defined momentum, p = mv, which is defined by mass m and velocity v at any given moment. This is the typical...
Electric Field of Two Equal and Opposite Charges
Atoms generally contain the same number of positively and negatively charged particles, protons, and electrons. Hence, they are electrically neutral. However, the centers of the positive and negative charges do not always coincide. In such a scenario, the electric field of an atom may not be zero.
A separation of the positive and negative charges can lead to a weak, remnant effect of the positive and negative charges. The expectation is that the more the distance between the positive and...
A separation of the positive and negative charges can lead to a weak, remnant effect of the positive and negative charges. The expectation is that the more the distance between the positive and...
The Electrical Double Layer
In the region where two bulk phases meet, an intricate electric charge distribution arises due to charge transfer, ion adsorption, molecular orientation, and charge distortion. This complex distribution is commonly referred to as the electrical double layer.When a solid electrode interfaces with ions in an electrolyte solution, the speed of electron transfer dictates the rates of oxidation and reduction. The electrode acquires a charge through the escape of atoms into the solution as cations or...
Fermi Level Dynamics
The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...

