Shamjid,

In order to get the best range for the more accurate determination of of the solar cell parameters. let us return to the original one diode equation representing the illuminated I-V characteristics.

It is so that the the effect of the Rsh is very pronounced around the short circuit  point and reverse bias of the solar cell and the cell current can be approximate by 

I= Isc- V/Rsh., so the best range to determine Rsh is around the shortcircuit and reverse bias condition.

The reverse saturation current and the ideality factor are best determined where both the effect of the RS and Rsh is negligible. This is the intermediate forward biasing of the solar cell junction That is where the dark current of the diode is much larger than the the current in the shunt resistance and the voltage drop on the series resistance IRs

This method is just an approximation - smart and quick, but just approximation. 

I was not going deeper into this interesting paper, but I am certain it required some sort of expansion of diode equation to simpler form of equations (e.g. to trigonometric functions with Fourier transform).

Exponential nature of diode equation makes it difficult to approximate it well in both positive and negative bias regimes. It may be a source of your issue.  

Good approach to address it experimentally would be to make a physical model of discrete element model of solar cell (fig1 in referenced paper) with elements of known and sensible values. Then take an IV curve of this system in 0-1 and -1-1 ranges and compare results against known values of parameters.

Shamjid,

In order to get the best range for the more accurate determination of of the solar cell parameters. let us return to the original one diode equation representing the illuminated I-V characteristics.

It is so that the the effect of the Rsh is very pronounced around the short circuit  point and reverse bias of the solar cell and the cell current can be approximate by 

I= Isc- V/Rsh., so the best range to determine Rsh is around the shortcircuit and reverse bias condition.

The reverse saturation current and the ideality factor are best determined where both the effect of the RS and Rsh is negligible. This is the intermediate forward biasing of the solar cell junction That is where the dark current of the diode is much larger than the the current in the shunt resistance and the voltage drop on the series resistance IRs

Abdelhalim, Maybe there's something I am missing in your excellent reply. Perhaps I am confusing the meaning of your symbols? If Rsh is the shunt resistance, then I must be the current out of the cell and Isc must be the photocurrent; so you have Isc = I + V/Rsh. But under short circuit conditions V ~ 0 so Rsh could be almost anything, and won't affect the output current much. Conversely, under open circuit conditions when I ~ 0 , Rs could be almost anything and won't affect the output voltage; rather the opposite of what you're saying. This makes sense if your meanings of Rs and Rsh are reversed. Can you explain a bit more please?

Tonny,

I am very happy with your comment on my answer. 

It is so that the shunt resistance is evaluated by the slope of the I-V curve of the solar cell at the short circuit condition. Its value is the inverse of the slope of the I-V curve at V=0. This fact can be obtained by differentiating the the equation which you gave at the short circuit. According to your equation: absolute l value of dI/dV= 1/ Rsh.

The same holds near the open circuit condition where any perturbation dI will pass through Rs and cause a voltage increase of dV=dI Rs while it will very slightly affect the diode voltage since the diode voltage changes logarithmic ally with the current.

The whole picture may get more clear if we consider that the illuminated call current is a dark diode current shifted down by the short circuit photocurrent current. So, with reference to the the short circuit current, the cell current appears as a the dark diode current.

My best wishes to you

Well, if you are dealing with measurements obtained from a large-area solar cell where a significant part of the series resistance is of distributed nature (as it is the case for wafer-based silicon solar cells), then you're missing something important: For such cells, the effective value of the distributed series resistance varies along the I--V curve. (I can tell because it's one of my main research topics -- see below!)

This effect is known for many decades already, but it is widely ignored by the community. For further reading I recommend my 2013 SiliconPV paper "Injection-level Dependent Series Resistance: Comparison of CELLO and Photoluminescence-based Measurements" (https://www.researchgate.net/publication/275112445). Explicit lumped series resistance measurement results that exhibit this effect very clearly can be found in the 2014 EU-PVSEC proceedings paper "Ohmic loss analysis for lateral balancing currents by CELLO and photoluminescence measurements" (https://www.researchgate.net/publication/283257440). Don't hesitate to ask further questions, I'll be happy to answer them.

Article Injection-Level Dependent Series Resistance: Comparison of C...

Conference Paper Ohmic loss analysis for lateral balancing currents by CELLO ...

Please be aware that the effect of the series resistance varying along the I--V curve was already noted by Wolf & Rauschenbach in their 1963 paper "SERIES RESISTANCE EFFECTS ON SOLAR CELL MEASUREMENTS" (https://www.researchgate.net/publication/223585317); the full text is available from Sinton instruments (http://www.sintoninstruments.com/PDFs/wolf-aec61-seriesresitance-searchable.PDF).

In their Fig. 9(a) and in Table 1 the variation of the series resistance along the I--V curve is shown for one specific cell.

Article Series resistance effects on solar cell measurements

Hey Shamjit!!

Can you please share the code or reference files related to it...as i am working on the same project.

I want it for reference just in case. It would be helpful.

Thanks :)

Dear all,

Are these models and MATLAB codes are also applicable for hallide perovskite based solar cells and inoganic perovskite solar cells (BiFeO3). Can anyone send me the MATLAB code. I'll be highly thankfull.

Thanks in advance.

Dear all,

The paper bellow presents a simple method to extract the PV cell parameters:

Article A new method to extract the equivalent circuit parameters of...