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IamSmooth

Mon Nov 19 2007, 01:45AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I was watching TLC or Discovery (not sure which) and it was showing a large solar panel being assembled from multiple, octagon crystals. Each individual cell was about the size of my palm, and there were many connected in series and parellel, yielding a 150 W (give or take) panel.

Is it possible for the homeowner to build a panel from scratch? I should be more specific. I don't want to just solder the cells. I would like to make the crystaline cells themselves. BTW, I am not talking about heating a piece of copper and putting the oxide in saltwater.

Are we talking about a large industrial process? This link makes me think this is beyond my lone ability:

...

Mon Nov 19 2007, 03:30AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

You can create solar cells through a series of chemical processes that could be done at home, but the efficiency isn't worth using (my dad worked on this for his thesis)

To make even the cheapest cells out today, you need the same tools that are required for making computer chips. The process is almost identical (I work at a company that makes solar cells atm).

To go into further detail... The process starts with good ole dirt, (SiO2), which is then reduced to just Si. From there you use some trade secrets to get it to about 99.9999999% pure silicon (8-12 9's of purity). Then you melt it, and draw a seed crystal through the melt, which creates a large single Si crystal. You also have to add in a few ppb of a dopant at this point. Luckly for you, there are lots of companies that specialize in this, and you can buy 'wafers' all ready to go for a reasonable cost (try ebay)

From there, all you need to deposit a layer (or more realistically several layers) of a different dopant onto the surface of the wafer to create the p/n junction. Unfortunately, they way that this is done is by heating the wafer to about 1000C in a hydrogen environment, and let a very small about of a metal hydride (phosphine for P arsine for As ammonia for N etc) into the chamber, which decomposes upon touching the wafer, leaving a very thin layer of the dopant (can be as thin as a few angstroms).

Then you silkscreen on a layer of metal for the electrodes, solder into a panel, and you are set to go!

philstesla

Mon Nov 19 2007, 12:28PM

Registered Member #990 Joined: Sat Sept 08 2007, 05:44PM
Location: North Staffordshire, UK
Posts: 7

Here's a link to a company that makes a Graetzel cell kit:

This is probably the easiest type of PV cell to construct at home. It is possibly the only type you could successfully build and hope to generate real power from. Efficiency is relatively low, but the production costs are so low, that's irrelevant.

As the previous poster suggests, making your own semiconductor PV isn't really practical. Given my own experiences of making silicon diodes at uni, even with considerable resources (prepared wafers, cleanroom, good vacuum aparatus) this type of manufacture is very hard indeed and not for the faint hearted.

Bjørn

Mon Nov 19 2007, 12:43PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

0.43% efficiency is a bit on the low side even for a cheap photovoltaic cell. Does anyone know how much it can be improved with better construction?

Electroholic

Mon Nov 19 2007, 03:01PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

Also float-zone silicon is usually used instead of ones grown from the Czochralski process.

ShawnLG

Mon Nov 19 2007, 04:25PM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

"To make even the cheapest cells out today, you need the same tools that are required for making computer chips. The process is almost identical (I work at a company that makes solar cells atm)."

Not anymore. There is new technology out there that can print out solar cells much cheaper than traditional solar cell manufacturing methods.

ragnar

Mon Nov 19 2007, 08:52PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

ShawnLG wrote ...

Not anymore. There is new technology out there that can print out solar cells much cheaper than traditional solar cell manufacturing methods.

http://www.technologyreview.com/Energy/17025/

Wow, will it bring down global capitalism, start a second industrial revolution and save the environment, too? That's the last spin I saw on printing things. =P

To be frank, the end result may be cheaper PV cells, but the fact remains that the production IS an inherently complex process (semiconductor fabrication), and can't be done at home. The "new technology" is not about to put PV-panel manufacturers out of business or allow you to whip up PV cells on your home inkjet.

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