New nanomaterial increases yield of solar cells

Aug 26, 2013
New nanomaterial increases yield of solar cells
Linked quantum dots - In the new nanomaterial two or more electrons jump across the band gap as a consequence of just a single light particle (arrow with waves) being absorbed. Using special molecules the researchers have strongly linked the nanospheres (quantum dots) as a result of which the electrons can freely move and an electrical current develops in the solar cell.

Researchers from the FOM Foundation, Delft University of Technology, Toyota Motor Europe and the University of California have developed a nanostructure with which they can make solar cells highly efficient. The researchers published their findings on 23 August 2013 in the online edition of Nature Communications.

Smart nanostructures can increase the yield of . An international team of researchers including physicists from the FOM Foundation, Delft University of Technology and Toyota, have now optimised the so that the solar cell provides more electricity and loses less energy in the form of heat.

Solar cells

A conventional solar cell contains a layer of silicon. When sunlight falls on this layer, in the silicon absorb the energy of the (photons). Using this energy the electrons jump across a '', as a result of which they can freely move and electricity flows.

The yield of a solar cell is optimised if the is equal to the band gap of silicon. Sunlight, however, contains many photons with energies greater than the band gap. The excess energy is lost as heat, which limits the yield of a conventional solar cell.

Nanospheres

Several years ago the researchers from Delft University of Technology, as well as other physicists, demonstrated that the excess energy could still be put to good use. In small spheres of a the enables extra electrons to jump across the band gap. These nanospheres, the so-called , have a diameter of just one ten thousandth of a .

If a light particle enables an electron in a quantum dot to cross the band gap, the electron moves around in the dot. That ensures that the electron collides with other electrons that subsequently jump across the band gap as well. As a result of this process a single photon can mobilise several electrons thereby multiplying the amount of current produced.

Contact between quantum dots

However, up until now the problem was that the electrons remained trapped in their quantum dots and so could not contribute to the current in the solar cell. That was due to the large molecules that stabilise the surface of quantum dots. These large molecules hinder the electrons jumping from one quantum dot to the next and so no current flows.

In the new design, the researchers replaced the large molecules with small molecules and filled the empty space between the quantum dots with aluminium oxide. This led to far more contact between the quantum dots allowing the electrons to move freely.

Yield

Using laser spectroscopy the physicists saw that a single photon indeed caused the release of several electrons in the material containing linked quantum dots. All of the electrons that jumped across the band gap moved freely around in the material. As a result of this the theoretical yield of solar cells containing such materials rises to 45%, which is more than 10% higher than a conventional solar cell.

This more efficient type of solar cell is easy to produce: the structure of linked nanospheres can be applied to the solar cell as a type of layered paint. Consequently the new solar cells will not only be more efficient but also cheaper than conventional cells.

The Dutch researchers now want to work with international partners to produce complete solar cells using this design.

Explore further: Researchers glimpse pathway of sunlight to electricity

More information: Sandeep, S. et al. High Charge Carrier Mobility Enables Exploitation of Carrier Multiplication in Quantum-Dot Films, Nature Communications (23 August 2013). DOI: 10.1038/ncomms3360

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Shakescene21
2.5 / 5 (2) Aug 26, 2013
"This more efficient type of solar cell is easy to produce: the structure of linked nanospheres can be applied to the solar cell as a type of layered paint. Consequently the new solar cells will not only be more efficient but also cheaper than conventional cells."

Wow! The rate of technological progress in Photovoltaics is amazing.
I'm somewhat optimistic that we'll solve our Global Warming problem by making renewable energy cheaper than fossil fuels. When coal becomes more expensive than renewables, it will stay in the ground.
Soylent_Grin
2.3 / 5 (3) Aug 26, 2013
When coal becomes more expensive than renewables, it will stay in the ground.


Only after decades of whining, subsidies, lamentations about a way of life and culture vanishing, and "too big to just go away" bailouts.
Osiris1
4 / 5 (1) Aug 26, 2013
Our coal..and oil...have their uses, as lubricants until force field frictionless 'motors' become a reality. ....and as rocket fuel until we have to good sense to use fusion/ionic propulsion for direct earth to space travel and return.
djr
1 / 5 (1) Aug 26, 2013
"Only after decades of whining, subsidies, lamentations about a way of life and culture vanishing, and "too big to just go away" bailouts"

I think you are right Soylent - they will not go quietly into the night. I suspect that very soon the numbers are going to be undeniable - and then the utilities, and energy companies will have no choice but to embrace tomorrow's paradigm. I think that will actually be an exciting moment - as they will bring their massive financial clout into the political arena - and the train will be unstoppable. If they don't recognize the new paradigm - they will get left in the dust - I don't see them allowing that to happen.
djr
1 / 5 (1) Aug 26, 2013
Here is a really neat article on this issue. This author thinks that by 2030 - utilities, and ICE cars will be obsolete. Massive opportunities for people with vision to move into the void.

http://cleantechn...nosaurs/

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