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Nanocrystals May Provide Boost for Solar Cells, Solar Hydrogen Production

5 January 2006

Los Alamos National Laboratory scientists have discovered that a phenomenon called carrier multiplication, in which the absorption of a single photon by a nanocrystal quantum dot can generate multiple electrons, is applicable to a broader array of materials that previously thought.

The discovery increases the potential for the use of nanoscrystals as solar cell materials to produce higher electrical outputs than current solar cells, as well as possible application for the photocatalytic production of hydrogen.

In papers published recently in the journals Nature Physics and Applied Physics Letters, the scientists demonstrate that carrier multiplication is not unique to lead selenide nanocrystals, but also occurs with very high efficiency in nanocrystals of other compositions, such as cadmium selenide.

These new results also shed light on the mechanism for carrier multiplication, which likely occurs via the instantaneous photoexcitation of multiple electrons. Such a process has never been observed in macroscopic materials and it explicitly relies on the unique physics of the nanoscale size regime.

Carrier multiplication actually relies upon very strong interactions between electrons squeezed within the tiny volume of a nanoscale semiconductor particle. That is why it is the particle size, not its composition that mostly determines the efficiency of the effect. In nanosize crystals, strong electron-electron interactions make a high-energy electron unstable. This electron only exists in its so-called 'virtual state' for an instant before rapidly transforming into a more stable state comprising two or more electrons.

—Lead project scientist Victor Klimov

The Los Alamos findings point toward practical photovoltaic technologies that may utilize such traditional solar cell materials as cadmium telluride, which is very similar to cadmium selenide.

Other interesting opportunities may also be associated with the use of carrier multiplication in solar-fuel technologies and specifically, the production of hydrogen by photo-catalytic water splitting. The latter process requires four electrons per water molecule and its efficiency can be dramatically enhanced if these multiple electrons can be produced via a single-photon absorption event.

Research on carrier multiplication at Los Alamos is funded by the DOE’s Office of Basic Energy Sciences and by Los Alamos’ Laboratory-Directed Research and Development (LDRD) program.

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January 5, 2006 in Hydrogen, Research, Solar | Permalink | Comments (5) | TrackBack (4)

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Comments

I did a write-up on 'quantum dots' - i.e. nano-scale semiconducting crystals - back in October. Good to see more research is being published. These could be truly revolutionary for solar power and could help realize PVs of up 65% efficiency in the future. That part about using quantum dots for solar cracking of water for hydrogen is interesting as well. Lots of potential here...

Since you seem to be in the know how far in the future are we talking about? Is this 1 year or 10?
Thanks,
Bob

Any idea on the cost per KW of those new PV?


This is very excieting news. Getting evan 50% yeild would be outatanting. Right now a 10-15% use of direct sunlight is all we have acheived. I hope that this technology does not become,"The next thing in solar innovations". I hope that it is going to be produceable in a relativly short time and for a cost that will not be too expensive. So, that electricity could be a everyday thing in some parts of the "third world countries" and here at home when we have a Katrina like disater.

Frank

sir the informations are very nice. & i need more informations about the nanotechnology in the development of solar energy .if u can means please send me complete details to my id or just u inform me the site .since it is more use full to my project.(I am a student)

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