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question on cutting a large solar cell into smaller ones to get a higher voltage?

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Posted by mark.beck1 on July 9, 2007, 5:35 pm
 
Hi,

I'd like to request some hints on the topic. How do I cut a solar cell
efficiently? cut-off grinding
or just treat like glass (accurately defined breaking).

thanks in advance,

Mark


Posted by Loren Amelang on July 9, 2007, 7:35 pm
 
On Mon, 09 Jul 2007 10:35:29 -0700, mark.beck1@vodafone.de wrote:


Assuming you have single crystal cells...  Silicon wafers "want" to
break along straight lines defined by their crystal structure, but
unless your breaking force is exactly even and perfectly aligned, the
edges often veer off a bit in one direction or another. I don't know
if the crystal angle of solar grade wafers is distinguishable from
flats or notches, if they even exist on yours.

To cut a wafer wherever you want, despite the crystal structure, you'd
need to score it with a thin diamond wheel (or laser) and then snap
it, or just (very gently) saw it all the way through. I've never tried
a glass cutter, but I imagine it would start a break along the crystal
lines long before it made a score in the surface.

Loren

Posted by R.H. Allen on July 9, 2007, 11:09 pm
 mark.beck1@vodafone.de wrote:

Presumably you're talking about silicon solar cells. The best way to go
about it is generally to saw it with a dicing wheel. If you don't have a
dicing saw you can score it with a diamond scribe or similar (I suppose
a glass cutter would probably work, though I haven't tried it myself).
Either way, cut from the rear and don't cut all the way through. When
finished, carefully break along the cut. It is much more difficult for
multicrystalline silicon than for single crystal, but either way you're
liable to wreck a few cells along the way.

You'll need to plan your cuts carefully if you are to maintain places to
solder on both the front and back of the cut pieces. Also, cutting is
likely to degrade cell performance slightly even if you do a perfect job
of it. Unless your solar cell is unusual, cutting it from the front will
lead to greater degradation and more failures than cutting from the rear.

The above advice holds for the vast majority of silicon solar cells on
the market, but there are a few for which it will not hold. Most of the
exceptions most likely cannot be cut without ruining them (e.g.,
Sunpower's cells). Thin film panels also most likely cannot be cut
without ruining them.

Posted by Bob on July 11, 2007, 1:20 pm
 On Jul 9, 10:35 am, mark.be...@vodafone.de wrote:

Cutting the solar cell is only part of the problem. You also need to
be able to attach electrical leads to the cell, and this can be
tricky. Regular solder usually does not work well, but pure Indium
might be a possibility. Conductive epoxy is another choice, but it
must be heavily loaded with silver to be conductive enough to carry
current.

Bob


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