Nanocones could be key to making inexpensive solar cells

June 5, 2012 by Lisa Zyga, Phys.org feature

(a) Fabrication process of the solar cells, in which silicon nanocones are coated with a polymer. (b), (c), and (d) show scanning electron microscope images of the nanocones after each step. Image credit: Jeong, et al. ©2012 American Chemical Society
(Phys.org) -- One of the biggest challenges facing the silicon photovoltaic industry is making solar cells that are economically viable. To meet this goal, the module cost, which is currently about $1/watt, needs to be decreased to just half that. Much of this cost comes from the silicon material and the expensive fabrication processes often used. In a new study, a team of scientists and engineers has demonstrated that a hybrid solar cell covered in silicon nanocones and a conductive organic polymer can address both cost-cutting areas while providing excellent performance.

The researchers, led by Professor Yi Cui and Professor Michael D. McGehee from Stanford University, have published their study in a recent issue of .

The hybrid ’ use of nanoscale texturing has two advantages: it improves light absorption and reduces the amount of material needed. Previous nanoscale texturing of solar cells has involved nanowires, nanodomes, and other structures. Here, the researchers found that a nanocone structure with an aspect ratio (height/diameter of a nanocone) of around one provides an optimal shape for light absorption enhancement because it enables both good antireflection (for short wavelengths of light) and light scattering (for long wavelengths).

In previous designs using nanoscale texturing, the space between structures has normally been too small to be filled with polymer, so a full second layer is required. But the tapered nanocone structure demonstrated here allows for the polymer to be coated in the open spaces, eliminating the need for other materials. By forming this nanocone/polymer hybrid structure with a simple, low-temperature method, processing costs are also reduced.

After testing the solar cell and making some improvements, the researchers produced a device with an efficiency of 11.1%, which is the highest among hybrid silicon/organic solar cells to date. In addition, the short-circuit current density, which indicates the largest current that the solar cell can generate, is only slightly lower than the world record for a monocrystalline silicon solar cell, and very close to the theoretical limit.

Due to the hybrid silicon nanocone-polymer solar cells’ good performance and inexpensive processing, the researchers predict that they could one day be used as economically viable photovoltaic devices.

Explore further: USC team develops promising polymer for solar cells

More information: Sangmoo Jeong, et al. “Hybrid Silicon Nanocone-Polymer Solar Cells.” Nano Letters. DOI: 10.1021/nl300713x

Journal reference: Nano Letters search and more info website

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13 comments

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Birger
not rated yet Jun 05, 2012
Good news. Of course, we need confirmation that the cells have sufficient life spans for commercal applications, but this looks good :-)
yoatmon
not rated yet Jun 05, 2012
Well, it certainly doesen't look bad but it's far off from the 22 to 23% efficiency presently achieved from mono-crystalline devices.
fmfbrestel
not rated yet Jun 05, 2012
Efficiency doesn't matter nearly as much as $/Watt, within certain limits of course. Obviously need a certain amount of watts total from the space available (the area of my roof must support my electrical needs, for example), but so long as that constraint is met, CREAM (cash rules everything around me) applies.
Terriva
1 / 5 (1) Jun 05, 2012
The application of nanocones or nanorods in solar cell technology is not new at all but so far I didn't met with some practical application of it. Such a nanostructures are increasing physical surface of cells, thus making them less prone to the contamination, photooxidation and related degradation.
dschlink
not rated yet Jun 05, 2012
With installation costs accounting for 70-80% of a home system, an innovation in panel design to simplify setup is what is really needed. Lower cell costs are much more important for large systems, of course.
Eikka
5 / 5 (1) Jun 05, 2012
15 years ago, denialists were insisting that $1.00 a watt was impossible to achieve.


And it was - for 15 years. Hindsight is always 20/20.

aironeous
not rated yet Jun 05, 2012
Stuff like this won't happen if you let China gain a solar panel monopoly in the US. Because once they drive out of business all of the US solar manufacturers they will raise the prices because that is their plan. Their solar companies are only surviving because of communism subsidies and guess where they are getting all that money? From stealing our technology and counterfeiting our brands and stealing our trade.
baudrunner
not rated yet Jun 05, 2012
The shape increases surface area. This principle applied to ion plasma thruster cathodes for rocket engines like the VASIMIR would also increase efficiency substantially per unit area.
Cave_Man
1 / 5 (1) Jun 05, 2012
Despite the obvious devious military downside, i think these nano-cones, at least similar ones would be perfect for an element of microwave propulsion.

If you could make the system out of a layer of microwave absorbing nano cones feeding into a substrate of superconducting mat. which in turn feeds the initial microwaves. You extract thrust from the microwaves by making a macro cone or hundreds of smaller cones and feeding microwaves from central source. Assuming of course that absorption doesn't interfere with the force exerted by the microwaves.

You still needs lots of energy but not nearly as much as burning thousands of tons of liquid fuel. Could be accomplished by a liquid fuel cell, or series etc.
hyongx
1 / 5 (1) Jun 05, 2012
Nanocones could be key to making inexpensive solar cells


Nanocones could be key to making delicious nano-ice-cream-cones.

Now just for the nano-cows for the nano-cream.
axemaster
1 / 5 (1) Jun 05, 2012
The shape increases surface area. This principle applied to ion plasma thruster cathodes for rocket engines like the VASIMIR would also increase efficiency substantially per unit area.

It's a lot more than that. The cones allow quantized modes between them at a wide range of frequencies, hence the increased absorption bandwidth. Also, they called it "antireflective" because the cones tend to cause multiple reflections on the surface for short wavelengths, increasing the absorption further.
antialias_physorg
3 / 5 (2) Jun 06, 2012
Well, it certainly doesen't look bad but it's far off from the 22 to 23% efficiency presently achieved from mono-crystalline devices.

But these suckers aren't cheap.

With installation costs accounting for 70-80% of a home system, an innovation in panel design to simplify setup is what is really needed.

Solar shingles would be one way to go (they already on the market). If you need to resurface your roof anyhow then adding solar to it gives you next to no additional installation cost.

After a bit of googling:
An average home uses (in the US) 18000kWh of power per year.
A 2kW rated photovoltaic system produces about 1500 to 1600kWh per year (in the UK).
Size of a commercial 2KW system: 35 by 50 cm.

So you shouldn't be too worried about space requirements - even if the efficiency of the new type is lower (i.e. the area is bigger). That should still fit on a roof.
Isaacsname
not rated yet Jun 11, 2012
Wouldn't faceted minarets at the tops help trap light more efficiently ?

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