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Related Concept Videos

Semiconductors01:22

Semiconductors

There is variation in the electrical conductivity of materials - metals, semiconductors, and insulators that are showcased with the help of the energy band diagrams.
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
Types of Semiconductors01:20

Types of Semiconductors

Intrinsic semiconductors are highly pure materials with no impurities. At absolute zero, these semiconductors behave as perfect insulators because all the valence electrons are bound, and the conduction band is empty, disallowing electrical conduction. The Fermi level is a concept used to describe the probability of occupancy of energy levels by electrons at thermal equilibrium. In intrinsic semiconductors, the Fermi level is positioned at the midpoint of the energy gap at absolute zero. When...
Carrier Generation and Recombination01:22

Carrier Generation and Recombination

Carrier generation is the process by which electron-hole pairs (EHPs) are created within the semiconductor. In direct-bandgap semiconductors, such as gallium arsenide (GaAs), this occurs efficiently when energy absorption prompts valence electrons to leap into the conduction band, leaving behind holes.
This process is given by the generation rate G and is efficient due to the conservation of momentum between the valence band maximum and conduction band minimum.
Indirect generation involves an...
Carrier Transport01:21

Carrier Transport

The generation of electrical current in semiconductors is fundamentally driven by two mechanisms: drift and diffusion. These processes are essential for the functionality and performance of semiconductor-based devices.
Drift Current:
The drift of charge carriers is started by an external electric field (E). Charged particles, such as electrons and holes, experience an acceleration between collisions with lattice atoms. For electrons, this results in a drift velocity (vd) given by:
Metal-Semiconductor Junctions01:24

Metal-Semiconductor Junctions

The contact of metal and semiconductor can lead to the formation of a junction with either Schottky or Ohmic behavior.
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
Biasing of Metal-Semiconductor Junctions01:27

Biasing of Metal-Semiconductor Junctions

Biasing metal-semiconductor junctions involves applying a voltage across the junction. Specifically, the metal is connected to a voltage source, while the semiconductor is grounded. This technique is essential for controlling the direction and magnitude of current flow in electronic devices, including diodes, transistors, and photovoltaic cells.
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...

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Related Experiment Video

Updated: Jul 26, 2026

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications
10:56

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

Published on: February 6, 2016

Electron and hole transfer from indium phosphide quantum dots.

J L Blackburn1, D C Selmarten, R J Ellingson

  • 1National Renewable Energy Laboratory, Golden, Colorado 80401, USA.

The Journal of Physical Chemistry. B
|July 21, 2006
PubMed
Summary

Hole transfer from indium phosphide (InP) quantum dots (QDs) to TMPD is efficient, while electron transfer to TiO2 occurs via surface states. This research clarifies charge transfer dynamics in InP QDs.

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Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode

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Synthesis of In37P20(O2CR)51 Clusters and Their Conversion to InP Quantum Dots
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Last Updated: Jul 26, 2026

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Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode
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Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode

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Synthesis of In37P20(O2CR)51 Clusters and Their Conversion to InP Quantum Dots
08:21

Synthesis of In37P20(O2CR)51 Clusters and Their Conversion to InP Quantum Dots

Published on: May 7, 2019

Area of Science:

  • Materials Science
  • Photochemistry
  • Nanotechnology

Background:

  • Colloidal indium phosphide (InP) quantum dots (QDs) are promising nanomaterials for optoelectronic applications.
  • Understanding charge transfer dynamics is crucial for optimizing QD-based devices.

Purpose of the Study:

  • To investigate electron and hole transfer mechanisms in photoexcited InP QDs.
  • To elucidate the role of surface states in charge transfer processes.

Main Methods:

  • Utilized photoluminescence quenching and time-resolved transient absorption (TA) spectroscopy.
  • Studied hole transfer to N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD).
  • Examined electron transfer to nanocrystalline titanium dioxide (TiO2) films.

Main Results:

  • Core-confined holes in InP QDs are effectively quenched by TMPD.
  • A new approximately 4-picosecond component was observed in the TA decay, indicating rapid hole transfer.
  • Electron transfer to TiO2 is predominantly mediated by surface-localized states on the InP QDs.

Conclusions:

  • Hole transfer from InP QDs to TMPD is a rapid and efficient process.
  • Surface states play a critical role in facilitating electron transfer from InP QDs to TiO2.
  • These findings provide insights into controlling charge transfer for advanced nanomaterial applications.