If we are talking about traditional p-n type solarcells, they physically can't do better than ~37% IIRC. There is just no way to avoid some (alot!) charge recombination. In addition there is a lot of solar energy that is not within the absorption curve.
I really hate it when people throw numbers around without a reference. All photovoltaics should be referenced to AM 1.5 (the typical energy that reaches the earth). The solar people all talk about photosynthesis as 'near 50%' but that is only over the narrow absorption range of the special pair and does not include any further electron transfer steps.
I have to concur that it is all about making them cheaper. That said, while you can trade effiency for cost, the who 'nanocrystal photovoltaics' died a quite death cause the charge transfer was just SO piss poor due to it being an amorphous device. Now if someone can figure out how to add some structure (chemical self assembly) then you might have something. As with most other hyped science I would not hold your breath.
Engineers are damn cleaver people and my bet is on the thin film amorphous silicon and cadmium telleuride ribbons being developed.
solarcell
What you seem to be missing is that the Sandia people were mixing three different colors of nanocrystals to get 'white' light. What the Vanderbilt folks did was using a SINGLE material. Thats the big deal. Early on, folks made nanocrystals using high temperature pyrolysis of dimethyl cadmium and selenium dissolved in a phosphine. There were two different emission features: the bandedge recombination and a large broad 'deep trap' feature. The deep trap feature was named for the nanocrystals precipitated from aqueous solutions which had lots of physical internal defects. The pyrolitic synthesis does not have any internal defects (well less than one per dot) Then came using cadmium oxide which was 'greener' and not pyrophoric like DMC. Read safer and easier to work with... Well part of the change from DMC to CdO was adding an amine into the solvent mix. When you add the amine the deep trap feature disappears. The deep trap feature is actually recombination of the excition (emission) where one of the charges was trapped to the surface. Since there are many different types of surface sites, you get a varity of states being emitted from. Well the Vandy folks made them SO small that the charges have no choice BUT to recombine on the surface and therefore take advantage of the multitude different energy surface states and therefore get 'white' light emission. Of course this is the most plausable guess. The paper doesn't prove anything.
QToad
Slashdot Mirror
If we are talking about traditional p-n type solarcells, they physically can't do better than ~37% IIRC. There is just no way to avoid some (alot!) charge recombination. In addition there is a lot of solar energy that is not within the absorption curve. I really hate it when people throw numbers around without a reference. All photovoltaics should be referenced to AM 1.5 (the typical energy that reaches the earth). The solar people all talk about photosynthesis as 'near 50%' but that is only over the narrow absorption range of the special pair and does not include any further electron transfer steps. I have to concur that it is all about making them cheaper. That said, while you can trade effiency for cost, the who 'nanocrystal photovoltaics' died a quite death cause the charge transfer was just SO piss poor due to it being an amorphous device. Now if someone can figure out how to add some structure (chemical self assembly) then you might have something. As with most other hyped science I would not hold your breath. Engineers are damn cleaver people and my bet is on the thin film amorphous silicon and cadmium telleuride ribbons being developed. solarcell
What you seem to be missing is that the Sandia people were mixing three different colors of nanocrystals to get 'white' light. What the Vanderbilt folks did was using a SINGLE material. Thats the big deal. Early on, folks made nanocrystals using high temperature pyrolysis of dimethyl cadmium and selenium dissolved in a phosphine. There were two different emission features: the bandedge recombination and a large broad 'deep trap' feature. The deep trap feature was named for the nanocrystals precipitated from aqueous solutions which had lots of physical internal defects. The pyrolitic synthesis does not have any internal defects (well less than one per dot) Then came using cadmium oxide which was 'greener' and not pyrophoric like DMC. Read safer and easier to work with... Well part of the change from DMC to CdO was adding an amine into the solvent mix. When you add the amine the deep trap feature disappears. The deep trap feature is actually recombination of the excition (emission) where one of the charges was trapped to the surface. Since there are many different types of surface sites, you get a varity of states being emitted from. Well the Vandy folks made them SO small that the charges have no choice BUT to recombine on the surface and therefore take advantage of the multitude different energy surface states and therefore get 'white' light emission. Of course this is the most plausable guess. The paper doesn't prove anything. QToad