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.
