# Current limit through solar cell (forward bias)

#### Sho

How much current can be forced through a photovoltaic (solar) cell before its performance starts to deteriorate? In certain accelerated lifetime testing 1.25xIsc is forced through a solar module while it sits inside a chamber (no incident light). Is there a theoretical limit to the amount of forward bias current pushed through this module? At some current, the module might get hot to cause deterioration of materials surrounding the solar cells. But once the current is turned off, will the solar module perform as it did before this test was started? Will there be a thermal runaway if the test is carried on for multiple hours?

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#### berkeman

Mentor
How much current can be forced through a photovoltaic (solar) cell before its performance starts to deteriorate? In certain accelerated lifetime testing 1.25xIsc is forced through a solar module while it sits inside a chamber (no incident light). Is there a theoretical limit to the amount of forward bias current pushed through this module? At some current, the module might get hot to cause deterioration of materials surrounding the solar cells. But once the current is turned off, will the solar module perform as it did before this test was started? Will there be a thermal runaway if the test is carried on for multiple hours?
Welcome to the PF.

Why would you want to force current in the reverse direction from the normal photocurrent?

#### Sho

I want to perform an experiment where I simulate outdoor module temperature indoors. Since the module will be running at Imp and the worst possible case would be at Isc outdoors, I can push Isc through to increase the module temperature indoors. But the ambient temperature indoors would not be the same so I want to push more current to heat it up even more. I just worry that there is a limit to the current and I will end up damaging the cells.

#### berkeman

Mentor
I want to perform an experiment where I simulate outdoor module temperature indoors. Since the module will be running at Imp and the worst possible case would be at Isc outdoors, I can push Isc through to increase the module temperature indoors. But the ambient temperature indoors would not be the same so I want to push more current to heat it up even more. I just worry that there is a limit to the current and I will end up damaging the cells.
That seems like a very artificial experimental setup, and I'd worry that you could get false failures or false passes.

You are wanting to do an accelerated life test on the solar panels? If so, I think you should look at doing the standard ALT or HALT (highly-accelerated life test) on the panels, and provide illumination on the order of full insolation. How big are these panels? Are they modular so that the size of the illumination lamps can be reasonable? You may be able to shine the lamps through a glass window of the HALT chamber to keep from breaking the lights while you stress the solar panels.

The ALT testing that we do on all of the products that we design here at my work is 85C at 85% relative humidity for 1000 hours at full power. If you pass that test, you have a pretty good idea that your product will be reliable for years in the field...

ALT -- https://en.wikipedia.org/wiki/Accelerated_life_testing

HALT -- https://en.wikipedia.org/wiki/Highly_accelerated_life_test

.

#### Sho

The goal of the test is not to see if cells are deteriorating. It is to check if a solar module can be used as a heating plate to achieve temperatures of around 60C indoors by forcing current through the cells. My question was to make sure that this does not lead to deterioration of cells in a drastic way that causes thermal runaway. Is there a safety limit to the amount of current that can be forced through?

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