PV Gap

Michael Said:

How to plan an experiment to find the internal resistance of a solar cell?

We Answered:

Measure the no-load voltage under some value of light.

Under the same light, add a load and measure the drop. Measure the current or use a known value in ohms for the load.

The internal resistance of the cell is the voltage drop across it divided by the current.

It would be best to make a series of measurements and plot them. You will probably find that the internal resistance varies with light intensity and perhaps load.

John said:

A solar cell doesn't have an internal resistance in the accepted sense. It behaves as a current source but if the cell is oen circuit, the current is diverted through the effective diode that forms the cell itself. Try increaing the laod resistance steadily from zero and measure the voltage across, and current through, the load. You will find that up to a certain value of load, the current is virtually constant but it then begins to fall off as the load is increased further. The cell behaves as a current generator with a diode shunting it.