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Before the NREL work, researchers had believed that silicon crystals small enough to produce the multielectron effect would be impractical as a photovoltaic material. At the nanoscale, the optical properties of silicon change so that it converts less light from the red end of the spectrum into electrons. As a result, any gains from more efficiently converting blue and ultraviolet light would be offset. Nozik and his colleagues found that the nanocrystals did not have to be as small as was previously thought, skirting this problem.
To be sure, the NREL work is only a first step. Making solar cells that take advantage of multielectron generation is a challenge. That's because the extra electrons are very short-lived, making it difficult to extract them from the nanocrystals to generate an electrical current. Indeed, this has proved so difficult that evidence of the effect has come from indirect methods such as spectroscopy rather than from current generated by a solar cell. The use of the indirect measures has led some prominent experts to question whether the extra electrons are actually being produced, although Nozik says that the effect has been confirmed using multiple techniques. Nozik and his colleagues are now working to make solar cells out of silicon nanocrystals--they're exploring a number of novel designs--and he says they've recently made direct measurements indicating that their cells are releasing multiple electrons per photon absorbed. (Their results have yet to be published.)
Honsberg is cautiously optimistic, calling the finding of the multiple-electron effect in silicon nanocrystals a breakthrough, but only "one breakthrough out of maybe three or four" needed to produce cheap, superefficient solar cells.
Arthur Nozik believes quantum-dot solar power could boost output in cheap photovoltaics.
Solar-power modules that concentrate the power of the sun are becoming more viable.
Hybrid with polymer solar cells
I would like to know if we could use silicon nanocrystals as dopants in P3HT:PCBM Bulk heterojunction solar cells and whether the efficiency thus achieved would be significant?
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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Siphon
152 Comments
Synergy
Wouldn't this be great to combine with other novel silicon technologies, such as Sliver Cells? Or silicon (amorphous) thinfilm maybe?
Reply
cripdyke
52 Comments
Re: Synergy
I think that, frankly, you failed to understand the article. This tech uses silicon NANOcrystals. Thin films are only valuable because they use less of the expensive pure silicon crystals grown to large sizes and thicknesses under exacting conditions.
Nanocrystals are even smaller than thin film, which amounts to slicing the expensive crystals very thin so as to use less of an expensive ingredient and thus keep cost of manufacture lower than otherwise.
Nanocrystals are in fact so much smaller as to make comparisons a joke, really. Large, pure crystals are not the raw material for nanocrystals. And the nanocrystals cannot be amorphous... because they are crystals.
Now on the upside, this tech not only gains from the advantages of efficiency inherent in producing different numbers of electrons based on the amount of energy in the striking photon, but since it doesn't start out as a pure crystal -thick disk or thin film- a manufacturer does not incur the expense of paying for the expensive pure-silicon-crystal-growth processes.
So, the "synergy" with these other techs is effectively already in this one: high efficiency from nano, low costs from avoiding using large amounts of large, pure crystals. And yet it is not synergy at all, nor is it something that we must research to apply. Nanocrystals are not merely thin, they are ridiculously small. "Nano" by definition generally refers to things that are no more than a tenth of a millionth of a meter (100 nanometers or 100nm) in at least 2 spacial dimensions. (Although some "nano" work is in the field of nanofilms that meet this requirement in only 1 dimension, thickness, and are designed to be spread over surfaces for much larger distances than 100nm, often even macroscopic distances.) For these crystals they meet the 100nm criterion in all 3 spacial dimensions. As well, it is impossible for a nanocrystal to be amorphous, in the sense of non-crystalline. If it's a nanocrystal, it's a crystal...just a small one.
Hope that helps.
Reply
Siphon
152 Comments
Re: Re: Synergy
Yes it does, thank you. Amorphous? What was I thinking, duh. Unless of course the nanocrystals were irradiated for long periods of time (but why would one do that?)
The extreme size of the crystals actually sounds very problematic for mass production. How do you deposit these things onto anything adequately and homogeneously? And if that could be done, how do the crystals degrade over time in real world conditions?
Reply
atsilver
1 Comment
Re: Re: Synergy
I aggree with Siphon on this last point (his/her second paragraph) and hope to see a reply soon (from concept to lab to technology and from here to commercially available products there is also a long way, sometimes unable to be completed). And this is not a minor affair, nor a problem of correct understanding of the article, but a practical point of view.
Reply
rocnewhope
1 Comment
Re: Synergy
I have a factory which make wind turbines, currently we make 5KW VAWT for some big company such as Chinamobile etc, and they want we supply them solar panel too, there is a Chinese guy show me some document and claim he has the exclusive power for produce this product in China and he ask us invest huge money, after meet with him I find he know nothing about technology and business, so, I'd like if you can tell me who has this technology or patents, if there is some possible I can contact with him(them) and discuss about if we can cooperate for start a company in China for make this product, we can invest huge money for this project.
regards
roc
rocnewhope01 at yahoo dot com
Reply
nafisahmed29
1 Comment
Synergy
Can you please help me with these question, i will be very thankful
1. As we know nanocrystalline silicon is having indirect band gap and hence having low absorption coefficient than its counterpart amorphous silicon. So, what should be the optimum thickness of the intrinsic layer required for the complete absorption of solar spectrum?
2. Why the particles with size 100nm or less are only called as nanoparticles?
Reply