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QUANTUM DOT SOLAR CELLS

May 3, 2017

 

The world’s energy needs drastically increased compared to previous decades due to urbanization and Industrialization.On behalf of this, developed nations are also exploring themselves in finding out the source of renewable energy. Among various renewable energy sources, solar energy is abundant in nature and clean. But, the cost incurred for harvesting the solar energy is expensive, so the researchers are trying hard to make the solar energy generation in low cost. Concentrating on increasing the solar cells efficiencies at low cost might be a probable way to reduce the cost of solar power generation.

 

To increase the solar cell efficiencies, researchers are interested in analyzing the functional properties of nanostructured materials such as quantum dots transition metal nanoparticles, Plasmonic nanostructures and Hybrid nano polymer solar cells. Among these experiments, this blog will emphasize on quantum dot solar cells for developing the solar cell efficiency.

 

The sun emits the radiation of a lower wavelength and higher energy and the radiation of a higher wavelength and lowers energy when it strikes on the electromagnetic material. When the light photon of high wavelength and low energy strikes on semiconductor, It doesn’t excite the electrons in the valence to conduction band. In the case of low wavelength and high energy photon strikes on semiconductor, the transition of electrons is possible and Photocurrent is produced. Solar cells have silicon semiconductors which have energy gap 1.1eV corresponds to band gap that transfers the single free electron referred to as an exciton.This leads to photocurrent generation which is a considerable output from the solar cell.

 

Quantum Dot Solar Cells: Photons with lower energies than the band gap do not excite the electrons from valence band. To overcome this, Quantum dot has the ability to tune the band gap which is desirable for solar cells in contrast to bulk semiconductor materials, where the bandgap is fixed. Their name comes from their appearance as little dots which are roughly around 1 to 10 nanometers in size.  Its special feature is changing the size of the dots leads to change in the size of the band gap. So, we can make us of Photon with lower energies for the transition of exciton without letting into ruin by reducing the size of the quantum dots. Theoretically, this could boost solar power efficiency from 20 % to as high as 65 %.This is possible because when a single photon is absorbed by a quantum dot, it produces more than one bound electron-hole pair, or exciton, thereby doubling normal conversion efficiency numbers seen in single-junction silicon cells. A great aspect of quantum dots manufacturing is that there are multiple methods to fabricate them easily and at low cost. These methods include lithographic techniques, epitaxial techniques, and colloidal synthesis.

 

As compared to conventional solar cells, the QD solars have the ability to absorb light from each and every part of the solar spectrum and this is not possible by the traditional solar cells. Although, the quantum dots incorporated solar cells produces additional Photocurrent but the development in Short-Circuit is well below the expectation and it has proven theoretically only. However, Efforts are taken rigorously to make a notable improvement in solar cell efficiencies.

 

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