What is the purpose of supplying voltage and current to solar cell during cell measurement?

[smercurio_fc]

---

@JackDunaway wrote:

Could we get this thread moved to the LabVIEW or DAQ forum? Thanks!

---

Ditto!

[subsolanus]

A photovoltaic IV curve tester is nothing but a big capacitor that is monitored for current and voltage during charging. After a charge cycle is completed it is dicharged in a controlled fashion. The process is fast enough that the power dumped during discharge is low.

[sflow]

Thanks Felix for nice explanation. Actually my company are not building any solar tester but currently we bought an full set of IV tester to integrate with our equipment. So, I need to have some views from experts as this is totally new for me.

Do you mean that positive and negative probes must be correct while probing on solar cell otherwise it will get damaged? By the way, what's gonna happen to tester results because the solar simulator is just on top of those probes?

Best regards,

SF

[F._Schubert]

Most of your questions should actually be answered by the manufacturer of your IV tester.

Reverse polarity isn't a too big problem when you use normal cells. You only need to be cautious when you customize the setup (if you completely do it on your own). In this case just don't test it with a calibrated reference cell (WPVS or VLSI), which will withstand less current and cost a bunch of money.

Concerning the probes: If you get shading of the cells due to the probes, you will measure a too low Isc (and Impp). For qualification of equipement you should get some cells measured at a calibration laboratory and then compare them in your IV tester.

This depends on the level of qualification you need for your equipement. If you just want to monitor the manufacturing process, you can accept such an error and just compare the cells to each other. However I work with calibration labs, so there we need to put in great efforts to get rid of such errors.

Felix

[sflow]

Good day Felix, hope you doing fine.

Negative on top and positive probes at bottom? I think I will test it with some sample cells first. There are around 25 probes on 1 contact bar. So, alignment of probes to cell should be perpendicular with solar cell to reduce any shadowing?

For the I-V tester, only a photodiode is provided instead of calibrated reference cell to feed back irradiance. Will this be ok? Normally for other manufacturers they are providing a reference cell along with their tester.

Thanks & best regards,

SF

[F._Schubert]

You are doing the right approach concerning contacting -> minimal shading.

Concerning the reference cell, the monitoring diode isn't a replacement. The diode allows to correct for irradiance stability, both as feedback for the lamp and for correction formulas according to the normative specifications (IEC). But if you want to compare your data to others (other equipement, other manufacturers), you need a tracability chain to the SI units. You basically can achieve this in two ways:

* Get a reference cell and have it calibrated by an accredited institution (this is normally how it is delivered). The problem you will face is the increadible long delivery times of reference cells (propably the reason you didn't got one).

* Have some of your standard cells measured by a accredited institution. Time for getting such a calibrated cell is still a bit high, but much less than for the reference cells (it's also cheaper). The downside is that your standard cell don't have any protection, so they will wear and after some time break. And you generally will be lower down the tracability chain, so the combine uncertainity is higher. But this is a good option to begin with, and maybe sufficient for a production line (I guess the major problem in the long term will be improper handling of these cells, they will break too easy and still are some 100s-$ worth).

Felix

[sflow]

Hello Felix, hope you are fine.

I have done some testing in university and the process is quite interesting. I was noticed that some manufacturer offering testing by using a huge flat metal panel. But some are using 2 row of probes for rear surface busbar contact. Will the result be same?

Best regards,

SF

[F._Schubert]

If done correctly, the bar probes should work as well. If they have a too big spacing, you will get the fill factor (FF) measured too low. The plate also allows a better thermal spread, so you can control the temperature more precisely.

But if you have back-side contacted cells (e.g. MWT, Thinfilm), you only can use the bar probes.

Felix