Hi! I am currently trying to use the curve-fitting toolbox to find values for solar cell specs such as the dark current saturation, shunt resistance, and so on. My equation is: -iP + iSat*(exp(38.66976*x/n)-1) +x/Rshunt = y , where x is the voltage and y is the current.
For those of you who may not know, the dark current saturation (iSat) is often extremely small, somewhere between 1e-15 and 1e-5. The toolbox seems to not work very well with such small numbers, it gives me numbers all over the place and often when I push the fit around by changing the restrictions on the variables it improves drastically. I was able to estimate the Rshunt, but the iSat and n values are giving me trouble. Is there any way to make the curve fitting toolbox work better with very small numbers?