Related Experiment Video
Updated: Oct 18, 2025
14:58
Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping
Published on: June 3, 2015
15.0K
Surface state-induced barrierless carrier injection in quantum dot electroluminescent devices
Hyeonjun Lee1, Byeong Guk Jeong2, Wan Ki Bae2
1Department of Chemical and Biomolecular Engineering, KAIST Institute for the Nanocentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
Nature Communications
|September 28, 2021
Summary
Surface states enable barrierless hole injection in quantum dot devices, even at low voltages. This finding offers a new design principle for efficient electroluminescent devices using nanocrystal emitters.
Area of Science:
- Materials Science
- Nanotechnology
- Solid-State Physics
Background:
- Quantum dot light-emitting diodes (QLEDs) have advanced significantly, utilizing hybrid organic-inorganic structures.
- A key challenge is understanding barrierless hole injection in devices with unfavorable energy landscapes, occurring below the band gap voltage.
Purpose of the Study:
- To investigate the underlying mechanism of barrierless hole injection in quantum dot devices.
- To elucidate the role of surface states and Fermi level alignment in facilitating charge carrier injection.
Main Methods:
- Analysis of energy landscape in quantum dot devices.
- Investigation of Fermi level alignment influenced by surface states.
- Theoretical modeling of electrostatic potential and carrier injection barriers.
Main Results:
- Barrierless hole injection is primarily caused by Fermi level alignment due to surface states.
- This alignment creates a macroscopic electrostatic potential gain, promoting hole injection into quantum dots.
- The energy level alignment effectively overcomes Coulombic attraction within the quantum dots.
Conclusions:
- Surface states are crucial for achieving barrierless carrier injection in quantum dots.
- The findings provide a generalized design principle for developing highly efficient electroluminescent devices based on nanocrystal emitters.
More Related Videos
Related Concept Videos
01:24Metal-Semiconductor Junctions
576
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...
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...
576
01:22Carrier Generation and Recombination
884
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...
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...
884
01:11P-N junction
758
A p-n junction is formed when p-type and n-type semiconductor materials are joined together. At the interface of the p-n junction, holes from the p-side and electrons from the n-side begin to diffuse into the opposite sides due to the concentration gradient. This diffusion of carriers leads to a region around the junction where there are no free charge carriers, known as the depletion region. The charge density within the depletion region for the n-side and p-side can be described by the...
758
01:16Biasing of P-N Junction
1.1K
The operation of a p-n junction diode involves various biasing conditions, including forward bias, reverse bias, and equilibrium.
In equilibrium, no external voltage is applied across the p-n junction. The depletion region is formed at the junction interface due to the diffusion of carriers, which leaves behind charged dopants, acceptors on the p-side, and donors on the n-side. These immobile charges create an electric field that prevents further diffusion of carriers. The related energy band...
In equilibrium, no external voltage is applied across the p-n junction. The depletion region is formed at the junction interface due to the diffusion of carriers, which leaves behind charged dopants, acceptors on the p-side, and donors on the n-side. These immobile charges create an electric field that prevents further diffusion of carriers. The related energy band...
1.1K
01:21Carrier Transport
638
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:
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:
638
01:27Biasing of Metal-Semiconductor Junctions
367
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...
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...
367