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Did an experiment and found that when the light intensity shinning onto the solar panel increases, the measured current increases while the measured voltage remains more or less constant with very little increments.

Anyone is able to explain why?

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  • \$\begingroup\$ You need to provide a schematic showing the experiment. \$\endgroup\$ – Andy aka Nov 5 '19 at 10:00
  • \$\begingroup\$ @Andyaka its basically a solar cell with the ends connected to a multimeter. I do not know the exact dimensions and specifications of the solar cell. \$\endgroup\$ – Wb16 Nov 5 '19 at 10:12
  • \$\begingroup\$ That depends on the load, have you by any chance used LED as load? \$\endgroup\$ – Dorian Nov 5 '19 at 10:34
  • \$\begingroup\$ @Dorian nope, only components are the solar cell and the multimeter. \$\endgroup\$ – Wb16 Nov 5 '19 at 10:36
  • \$\begingroup\$ Essentially "because that;s what solar cells do". You can read up on the physics thereof on numerous sites. A solar cell approximates to a voltage limited variable-constant [ :-)] current source. The current is about proportional to insolation (light energy input). What you are reporting is what you'd expect to see. \$\endgroup\$ – Russell McMahon Nov 5 '19 at 10:44
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A solar panel is essentially a diode and will generate an open circuit voltage in the 500-700 mV pr cell. Typically a lot of cells are connected in series to get a higher output voltage.

When the solar cell is hit by a photon, it makes a electron jump across the silicon junction with an energy equal to this voltage (dependent on the temperature and type of solar cell).

If more photons (more light) hit the solar cell more electrons will be released, resulting in a higher current but the same voltage.

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View a solar cell as a diode.

The diode equation has various constants. For default doping profiles, at room temperature, an increase of current of 2.718X (do you recognize that number?) requires only 0.026 volts increase.

2:1 current increase requires 18 milliVolt increase.

10:1 current increase requires 58 milliVolt increase.

With 10:1 current increase only causing 10% or 8% increase in voltage, the solar cell seems Constant Voltage.

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  • \$\begingroup\$ To clarify, at constant room temperatures, the saturation current will remain constant? \$\endgroup\$ – Wb16 Nov 8 '19 at 2:19

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