Solar cell grading (A, B, C, D)

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Solar cell grading (A, B, C, D)

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Solar cell grading (A, B, C, D)

With solar cells accounting for 60%+ of the solar panel manufacturing costs, solar cells are the number one component used to cut overall costs of a solar panel.

No need to say, it's important to ensure that a pv manufacturer isn't cutting costs on this precious part of your pv module.

From our experience, in the current market situation it's extremely difficult to source grade B solar cells.

Those cells are often used by quality pv manufacturers to run tests OR by louzy pv manufacturers to cut costs of the pv module.

The worrying question here is: where do all these grade B cells go?

 

How are grade (A, B, C, D) cells classified?

There's a lot of confusion between different grade solar cells. Any deviation is often graded as B, however a correct classification is complicated because there are dozens of different solar cell defects that can occur.

This post is a first attempt to design a classification (A, B, C, D)  of solar cells, and is a summary of a more in-depth report.

 

 

1. Grade A solar cells

Grade A cells are simply without any visible defects, and the electrical data are in spec.

The specifications of the cells can be measured with cell testing equipment.

The perfect grade A cell may still have a slight bend of <= 2.0mm and a tiny color deviation is permitted.

Below a grade A solar cell. Due to the light the color seems to deviate, but in fact, this is a flawless solar cell:

Grade A - solar cell

Grade A - solar cell

2. Grade B solar cells

Grade B cells have visible but tiny defects, and the electrical data are in spec.
The following visible defects are common:

  1. Slight bend of 2.0mm - 2.5mm
  2. Color deviation, Visible yellow area takes more than 1/4 area of total on the Surface
  3. Missing prints < 0.5mm
  4. Part of front Busbar missing, missing area ≤ W:0.5mm×L: 5mm
  5. Paste leakage, for a single area: 0.3mm - ≤2.0mm2
  6. Scratch, length 15-50mm
  7. Water marks, L<15mm,W<2mm

Here a couple of examples of Grade B solar cells:

Grade B solar cell - Color Deviation

Grade B solar cell - Paste Leakage

Grade B solar cell - Large Bend

3. Grade C solar cells

A Grade C solar cell has visible defects, and the electrical data are off-spec.
All solar cells with defects worse than Grade B can be classified as Grade C.

Or

A solar cell can be graded as C when the partly broken cell which could be cut into smaller pieces and re-used.

Here are a number of Grade C solar cell examples:

Grade C solar cell - chipped cell

Grade C solar cell - corner breakage

Grade C solar cell - Busbar Missing

Grade C solar cell - Missing Print

Grade C solar cell - Water mark

4. Grade D solar cells

A Grade D solar cell is broken and can not be cut in smaller cells. There's not much you can do with these..

Grade D solar cell

Comment Section

20 thoughts on “Solar cell grading (A, B, C, D)


By Reinier on 8 October 2013

Thank you for the post on solar cells grading. There's a lot of confusion about this topic, as for instance Grade B solar panels can mean a lot of different things..

When I purchase solar panels that look perfect but are somehow off-spec in terms of performance, how can I find out?


By Dricus on 10 October 2013

Hi Reinier,

The first thing that you can is request the flash test from the manufacturer where you bought your solar panels. The flash test results.

More info here about the flash test:
http://sinovoltaics.com/topics/solar-panel-flash-test/

If you're based in Europe and you don't fully trust your manufacturer, you can first request the flash test, and then send a random solar panel from this batch to a third part testing lab.

There are a dozen of companies that can perform such a test, some large ones are TUV Rheinland, TUV Sud, VDE, SGS and Intertek.

If you're buying solar panels in China, it's cheapest and efficient to perform this flash test in China.. Quality testing in China is relatively cheap and in case they're cheating you on the specs, you can always go back to the factory and solve it before your goods are shipped out.

A good third part inspection company in China is http://www.kisunsolar.com


By Neeraj Thakur on 27 September 2016

Dear Dicrus,
Your comments are valuable for me, thanks for sharing.


By Abhishek Jain on 12 October 2016

We are buyer of Solar cells broken wafers


By Hicham L. on 23 January 2014

Does anyone sell broken solar cells? We have a small pv manufacturing line in Northern Africa and
can re-use cells for smaller panels.

If you have these cells available, please let me know. Also Grade B or C as described in the article above
is suitable. Grade D solar cells seem to be too small..


By Dricus on 23 January 2014

Hi Hicham,

Every cell and pv module manufacturer has a certain percentage of solar cell breakage. Why don't you contact those manufacturers directly? This will likely give you the best price..


By Irvin M. on 15 June 2015

I'm worried that the panel manufacturer I'm buying from is using grade B solar cells while I'm paying for a Grade A product. Sometimes I spot small imperfections on the solar cells, even though it's hard to say if the panels classify as Grade A, B or C. This post helps even though i'm still worried 🙁


By John Theo on 25 June 2015

Hi Irvin,
I'm noticing the same: small imperfections on the solar cells of my panels.
The power seems to be fine, but the cell color sometimes differs from one cell to the other, and there are some silver spots here and there. Would that mean it's Grade B?
Grade C should be quite obvious and would also mean the power of your panel is below the rating.. J.T.


By Peter on 10 August 2015

What would be the typical price difference between a Grade A and a Grade B solar cell?


By Dricus on 13 August 2015

The price difference between Grade A and Grade B solar cells can easily be USD 0.05 - 0.10/W.. That's why it's so appealing for PV manufacturers to squeeze in Grade B cells..in a price competitive market, it's often the only profit they take.


By Niclas on 21 August 2015

Hi Peter,
it can be as big as 0.05-0.15USD/W, typically at least 0.1USD/W. However, Grade B solar cells are a bit more difficult to come by as many manufacturers want them 😉


By Sachin Tiwari on 21 September 2015

We purchased 280 Wp Solar Panels 3 years back for Grid Tie system with Voc of 40 around, now the Voc is coming out to be 25-28 Volts. what could be the reason, Initially the cells were of same color and without any visible defects, now the color is faded to Orangish tone. What to Do, any advice


By Dricus on 22 September 2015

Thanks for sharing the prob you have with your system. May I ask the brand of the module? And can you perhaps send over a photo? We'll have a look at it.


By Amara on 19 May 2016

Dear guys i have question about poly panel simply can be recognizance by looking but mono crystalline how can be find out


By Niclas on 20 May 2016

Usually, the wafers of mono c-Si cells are cut from a rather roundish silicon ingot and thus up having a rather octagonal shape, while poly/ multi c-Si cells are cut in square.


By Amara on 20 May 2016

Dear guys
i have question about poly crystalline cells simply can be recognizance B grade by looking but mono crystalline B grade almost cell is black, how can be find out whether B grade

my other question i have seen poly crystalline some panel panels cells lot of color diffracts each other cells it means that can be conclude grade B cells

also some poly panel cells are dark blue some panel cells light blue, why that color difference , by color cab be conclude cell grade ? some of the cell inside slightly can see design like this pic (https://www.google.lk/search?q=solar+cells&rlz=1C1CHWA_enLK648LK648&espv=2&biw=1366&bih=667&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj9y7e5x-fMAhXEg6YKHYf2BPAQ_AUIBigB#imgrc=J9o9atXfEmXcCM%3A ) if possibly explain me


By Niclas on 23 May 2016

Dear Amara,

recognizing the grading of a cell just by looking at it is not 100% sufficient: you can draw more certain conclusions by testing it, peering into that cell (EL). Note that the sample defects shown in this article at the example of poly cells can also be found with mono cells.

The color differences you refer to stem from differences in coating thickness when adding anti-reflective coating during PECVD (see here: http://sinovoltaics.com/solar-basics/solar-cell-production-from-silicon-wafer-to-cell/), the color itself however does not tell a lot about a cell's grade.


By Amara on 20 May 2016

Dear guys
how can trust solar panel behind specifications ?
is there any legal aground ?
there mention about efficiency percentage and current, voltage by those specification proximate can be check but but when panel working time those things can be change ?


By Niclas on 23 May 2016

Amara,

as with virtually any (electronic) product, there is the shiny marketing curtain. And sometimes (or even more often), there is the no-shiny reality behind that curtain...

The datasheet values are usually indicative and geared to test conditions (STC, NOCT etc.) that you will normally not find in the real world. In the end, it comes down to how much you trust a manufacturer and its quality. There is however no perfect production output, and even products from premium manufacturers can have some (or even more) flaws, so if there are concerns, quality testing is generally the way to go.


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Dricus
Dricus is co-founder of the Sinovoltaics Group and Director at 3rd party PV Quality Assurance company Kisun Solar. Dricus has been working in the PV industry in China for 7 years. During his time in China he set up and managed a complete solar panel factory for a Canadian publicly listed company in Shanghai. Main interests are solar innovations, PV plant development and PV quality. Connect with Dricus on LinkedIn