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Questions and Answers
What may lead to more efficient light harvesting and energy conversion in solar cells that incorporate quantum dots?
QDs
What does the absorption of one photon of light create in bulk semiconductors versus in quantum dots?
Multiple exciton generation in quantum dots results in a quantum efficiency greater than 100%.
True
In quantum dots, intermediate bands allow for absorption of light below the band gap without sacrificing ________.
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What is the definition of quantum dots?
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Which materials are typically used to compose quantum dots?
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Quantum confinement is more prominent in metals compared to semiconductors.
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Quantum dots are bandgap tunable by ____.
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What is epitaxial growth in relation to quantum dots?
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Which coordinating ligand is commonly used to functionalize the surface of quantum dots?
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Study Notes
Introduction to Quantum Dots
- Quantum dots (QD) are nanoparticles with unique optical and transport properties due to 3D quantum confinement.
- QDs are usually regarded as semiconductors, but some metals can also exhibit similar behavior.
Quantum Confinement
- Quantum confinement is the spatial confinement of electron-hole pairs (excitons) in one or more dimensions within a material.
- It leads to the formation of distinct energy states, increasing the energy bandgap.
- Quantum confinement is more prominent in semiconductors due to their energy gap in electronic band structure.
Quantum Dot Synthesis
Colloidal Methods
- Example: CdSe quantum dot synthesis using octadecene, trioctylphosphine oxide (TOPO), and selenium precursor.
Epitaxial Growth
- Epitaxial growth refers to the layer-by-layer deposition of monocrystalline films on a substrate.
- Techniques include laser ablation, vapor phase epitaxy (VPE), liquid phase epitaxy (LPE), and molecular beam epitaxy (MBE).
Applications of Quantum Dots
Biological Applications
- Biological tagging and labeling
- Labeling of cells and intracellular structures
- In vivo and in vitro imaging
- Pathogen and toxin detection
- Quantum dots have high quantum yield and photostability, making them suitable for biological imaging.
Light Emitters
- Quantum dots have been used to develop new materials for LEDs and laser diodes.
- Indirect gap semiconductors like Si can become efficient light emitters at the nanoscale due to quantum confinement.
- Epitaxial InGaN, used in blue LEDs, has high radiative-recombination efficiency due to self-assembled, localized In-rich clusters that behave like QDs.
Additional Applications
- Solar cells incorporating QDs may lead to more efficient light harvesting and energy conversion.
- Quantum dots can enhance solar cells through "hot carrier" collection, multiple exciton generation, and intermediate bands.
Studying That Suits You
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Description
This quiz covers the applications of quantum dots in biological DNA assays, microarrays, and BioMEMS. It discusses the use of QD-functionalized DNA for fluorescence detection and gene expression profiling.
