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Quantum Dot or Nanocrystalline Solar Cells

Quantum dot solar cells are basically nano crystalline cells. These cells used a thin layer of nano materials over the substrate. The substrate is usually made of silicon.

Efficiency of Quantum dot Solar cells

These cells are much more efficient than any other kind of cells. They can produce enormous energy from just a single photon of light. Photons are the packets of light. They can be considered as building blocks just like atom is the building block of matter.

Prediction of National Renewable energy laboratory 2005

In 2005 researchers and scientists predicted about the extraordinary capabilities of this emerging technology. They also claimed to be able to achieve an efficiency of 65% with quantum dot or nanocrystalline solar cells.

Formation of Nano crystalline or Quantum dot Solar cells

The formation of these solar cells includes following steps.

  • A silicon substrate is required first of all.
  • The silicon substrate can be obtained in any way through ingots or something else.
  • The cells are not totally made of nano material.
  • A thin coating of nano material has to be done over the substrate.

Spin coating

Recently, new and more advanced methods of developing nano crystalline or quantum dot solar cells have been established. Spin coating is the most important among these.

This name has been given to this process due to the involvement of spinning process in the formation of solar cells.

Steps involved in spin coating

This process involves following steps.

  • First of all a silicon substrate is required just like in any other process.
  • Nano crystalline material is obtained in solution form.
  • The solution form is then placed in a small quantity on the silicon substrate.
  • The substrate is spun and rotated at very high speeds.
  • This rotation and spinning effect forms a smooth and uniform layer of nano material over the silicon substrate.
  • Consequently, a very good and even coating is established which is our objective during the formation of nano crystalline or quantum dot solar cells.

Carrier multiplication

This is the reason behind all this improvement in efficiency with these solar cells. Conventional solar cells can excite just one electron per incident photon. But quantum dot or nano crystalline solar cells excite several electrons with each photon and thus create enormous amount of electrical energy.

Materials used in Quantum dot solar cells

The most common materials used in these cells are

  • lead selenide (PbSe),
  •  cadmium telluride (CdTe),
  •  titanium dioxide (TiO₂)
  •  lead sulfide (PbS)

In addition to these, polymer solar cells can incorporate quantum dot technology to create a hybrid kind of cell that is much more efficient and flexible than each of its constituents.

Future Horizons

In spite of all these advantages, the research in quantum dot technology is still in its early stages. There is a long way to go from laboratory to roof tops. But with the genius efforts of our scientists this gap will soon be overcome.