This document discusses quantum dots, which are semiconductors on the nanometer scale that obey the principle of quantum confinement. The energy band gap of quantum dots determines the wavelength of light they can absorb and emit, and this wavelength depends on the size of the dot. Solutions containing quantum dots of different sizes appear different colors because the particles absorb and emit light within the visible spectrum. Potential applications of quantum dots include improving solar cells, use in televisions, and medical imaging.

1. QUANTUM DOTS
Presented By:
Md. Nahid Hasan
ID: 161001008
Dept.: EEE
Course Code: EEE-309
GREEN UNIVERSITY OF BANGLADESH

2. Quantum Dots
• Quantum dots are semiconductors that are on
the nanometer scale.
• Obey quantum mechanical principle of
quantum confinement.
• Exhibit energy band gap that determines
required wavelength of radiation absorption and
emission spectra.
• Requisite absorption and resultant emission
wavelengths dependent on dot size.
Figure: Schematic plot of the single
particle energy band gap.

3. Quantum Dots Description
• The name “dot” suggests an extremely
small region of space. The number of free
electrons in the dot can be very small.
Figure: Band gap energy of quantum
dots vary with its size.

4. Energy Bands in Quantum Dots
Figure: The energy band gap associated with semi-conducting materials. In order
to produce electric current electrons must exist in the conduction band.

5. Confinement – Infinite Square Well Potential
Figure: Quantized energy levels of a particle in a box.

6. Solutions of Quantum Dots
Figure: Solutions of quantum dots of varying size. The variation in color
of each solution illustrating the particle size dependence of the
optical absorption for each sample. The smaller particles are in
the blue solution (absorbs blue), and that the larger ones are in
the red (absorbs red).

7. Application of Quantum Dot
• Special quantum dots could improve transparent solar cells.
• Shiny quantum dots brighten future of solar cells.
• Quantum dot TVs to be launched by mid-2014.
• Quantum materials now shipping size-optimized metallic oxide.
• Medical imaging and disease detection.

8. References

9. THANK YOU