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solar cell defects?

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Posted by Bernhard Kuemel on July 17, 2013, 4:59 pm
 
Hi asp, sec!

I bought 300 "Class/Grade A" solar cells [1]. Just when I wanted to
resell some of them I discovered that most of them (all that I checked)
have a few (about 2-6) complete or partial gaps in the finger traces
that pick up the electricity and forward it to the bus bars. There are
also marks on the edge that look like overheated spots:

http://www.bksys.at/bernhard/solarzellen/defects/-gallery.html  

Many of the gaps appear in sequential cells in the same position, so it
seems it's a fabrication mask error, not a shipping defect.

Are these significant defects? Do they reduce performance or life time?
Would you care about them?

I have a bunch of Grade B polycrystalline cells with no such defects.

Thanks, Bernhard



[1]
http://www.ebay.at/itm/121129695438?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649  



Posted by Cydrome Leader on July 17, 2013, 8:55 pm
 

Did you buy chinese solar cells off ebay?

are you surprised at what you got?

Posted by Bernhard Kuemel on July 17, 2013, 9:18 pm
 On 07/17/2013 10:55 PM, Cydrome Leader wrote:

At first I was worried, but now I think, maybe they produce their stated
power with these defects. It's typically no more than one open in a
finger, so each part is connected to a bus bar. Cost optimized.


Posted by Lu Wei on July 20, 2013, 12:34 pm
 On 2013-7-18 0:59, Bernhard Kuemel wrote:

These low efficiency mono-cells can't be grade A, or they are labeled 3
years ago. And I think there is a little error on the label: The
diagonal can't be 195mm (should be 200mm I think), or 17.75% efficiency
and 4.24W will not agree. Anyway it's really cheap and worth the price.

As to what you concerned, you have guessed quite right. The broken
finger bars come from electrode printing error (mostly attributed to bad
mask) , and the gray marks on the edge is actually not error, but normal
behavior of coating with some equipments. Since the label says "coating:
CT", I think it's Centrotherm, whose equipments are used largely, and do
leave such spots on cells. Strange though, such information is seldom
printed on labels.

Since these defects are formed before I-V testing, you don't need to
care about them, as long as the efficiency is labeled correctly. And
they don't reduce life time.

--  
Regards,
Lu Wei
PGP key ID: 0x92CCE1EA

Posted by Bernhard Kuemel on July 22, 2013, 8:57 am
 On 07/20/2013 02:34 PM, Lu Wei wrote:

They might be 3+ years old, I don't know. They are said to be surplus of
some people making solar panels.


Interestingly I got cells with 195 mm and 200 mm diagonal, both 156*156
mm square. It's only a little difference at the corners.

Bernhard

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