I have a hard time understanding the I-V curve of a solar cell. I dont understand how in an short circuit a current can happen although there is no voltage? Isn't voltage the requirement for a current, so if voltage is zero, current must be zero? Or is there another driving force behind the current?

Second, where does the voltage come from at all? I always thought the potential stems from the p-n junction but i read a few sources that tell me that the pn junction actually only serves to seperate the charges (if i understood correctly), i.e.: http://energyprofessionalsymposium.com/?p=22032 & https://www.pveducation.org/pvcdrom/solar-cell-operation/the-photovoltaic-effect

In the second link it states that for the voltage to increase the charges must build up? but how can they build up? arent they always connected? I am totally confused =)

kind regards

  • $\begingroup$ Please only ask one question per post $\endgroup$ Sep 9, 2020 at 11:30
  • $\begingroup$ A solar cell is a current source. You will get maximum current out if there is no external voltage to mess with the junction. $\endgroup$
    – Jon Custer
    Sep 9, 2020 at 13:21
  • $\begingroup$ @JonCuster so the voltage part of the IV curve shows external voltage applied to the cell and not the internal voltage provided by the cell? $\endgroup$
    – racctor
    Sep 9, 2020 at 14:02
  • $\begingroup$ @JonCuster, not just a current source. A more accurate model is a current source in parallel with a PN diode. With no external circuit connected, the current flows across the junction in the forward direction when the Sun shines, and the terminal voltage of the cell equals the forward voltage of the diode. You get power out of it by connecting an external circuit that drags the voltage down to where very little of the photo current is able to flow directly across the junction. $\endgroup$ Sep 9, 2020 at 15:16
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    $\begingroup$ @SolomonSlow - indeed, but I figured I'd better start the OP down a very different thought path from what they seemed to be envisioning. $\endgroup$
    – Jon Custer
    Sep 9, 2020 at 15:20

1 Answer 1


So, for anyone interested I found the solution to my problem. I didn't know that there is a difference between voltage and "electromotive force".

A short explanation can be found here: https://circuitglobe.com/difference-between-emf-and-voltage.html


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