# How can one determine the key characteristics of a solar cell from the $I$-$V$ curve?

I have recently measured the $$I$$-$$V$$ characteristics of several $$\rm Si$$ solar cell samples and am now attempting to extract the series resistance $$R_S$$; parallel resistance $$R_P$$; open circuit voltage $$V_{OC}$$; short circuit current $$I_{SC}$$ and fill factor.

From what I have read, I understand that $$V_{OC}$$ is the voltage across the cell, for zero current flow and $$I_{SC}$$ the current flowing for zero voltage across the cell. Fill factor is the ratio of IV at maximum power production to the product of $$I_{SC}$$ and $$V_{OC}$$. I am, however, struggling to determine these values from my data (one example of the plotted data is shown below, please note that the orders of magnitude on the axis are off); all other IV graphs I have seen, have had a very different appearance, starting from a plateau at $$I_{SC}$$, before decaying down into $$V_{OC}$$, allowing both to be easily determined, as well as the fill factor.

I also understand that $$R_S$$ is to be found from the ln(I)-V curve, by finding the variation between the high-current section of the graph and the best fit of linear mid-current section and then plotting this voltage deviation against I, whereupon the gradient yields $$R_S$$ (see below graph).

$$R_P$$ is to be found by taking the inverse gradient of the linear portion of the I-V plot approaching zero voltage.

My question, so to speak, is whether my above stated understandings are correct and also how to extract the fill factor,$$V{OC}$$ and $$I{SC}$$ from my graph.