solar cell defects?

[Bernhard Kuemel]

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

[Cydrome Leader]

Did you buy chinese solar cells off ebay?

are you surprised at what you got?

[Bernhard Kuemel]

Yes.

> are you surprised at what you got?

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.

[Lu Wei]

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

[Kevin McMurtrie]

In article <ks6ii5$8kq$1...@news.albasani.net>,

Those conductor breaks look harmless because there are no islands. The
edge colors are normal.

A problem with crappy solar cells is internal leakage. They'll perform
to spec in full direct sunlight but you'll get zero volts indoors or in
the shade. There's a lot of IR indoor near lamps and a lot of UV
outdoors in the shade so a decent solar cell still has some use without
direct light. You can always do a side-by-side comparison with a known
quality cell.
--
I will not see posts from Google because I must filter them as spam

[Bernhard Kuemel]

On 07/20/2013 02:34 PM, Lu Wei wrote:
> On 2013-7-18 0:59, Bernhard Kuemel wrote:
>> 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
>>
>>
>
> These low efficiency mono-cells can't be grade A, or they are labeled 3
> years ago.

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

> 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.

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

[Bernhard Kuemel]

On 07/21/2013 08:16 AM, Kevin McMurtrie wrote:
> Those conductor breaks look harmless because there are no islands. The
> edge colors are normal.
>
> A problem with crappy solar cells is internal leakage. They'll perform
> to spec in full direct sunlight but you'll get zero volts indoors or in
> the shade. There's a lot of IR indoor near lamps and a lot of UV
> outdoors in the shade so a decent solar cell still has some use without
> direct light. You can always do a side-by-side comparison with a known
> quality cell.

My cells have 0.46 V and 39 mA inside in the shade. I put them in a
stainless steel pan as backside contact and touched the middle bus bar
with a multimeter probe. My desk is next to the window, it's a bright
day outside, no direct sun hitting my window, just some diffuse reflections.

Bernhard

[Lu Wei]

On 2013-7-22 16:57, Bernhard Kuemel wrote:

>> 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.
>
> 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.
>

17.75%, 156*156 and 195 diagonal will give 4.197W. The difference is
small but could not be mis-labeled. Maybe the package is not original.