The ideality factor n is one of the diode I-V characteristics parameters. It is an indicator of the recombination mechanisms ruling inside the diode. If the recombination occurs in the neutral regions of the diode n=1. and if the recombination in the space charge region dominates, n=2. For diodes whose recombination at the hetero face is dominant n can be higher than 2. The ideality factor affects the fill factor of the solar cell and it is so the as n increases the fill factor decreases.

Mathematically the dark current of the solar cell= Id= Is exp V/nVt , with Vt is the thermal voltage.

For other solar cells irrespective of their structure or theory of operation if their i-v Curve can be be curve fitted by an equation like the above one, then one can equivalently assign an ideality factor of them.

Other wise, it is not necessary to describe the I-V curve with with an equation like that given above and therefore no need to define an ideality factor for them.

Best wishes

As you know ideality factor defines how good your diode is. Now, it depends on I, V, temperature and junction quality. At room temperature, higher value of ideality factor means the junction between two semiconductor (p-n junction) or metal semiconductor junction (schottky) is not good enough. This in turn determines the rectification property of the diode. But, in case of solar cells (however it is a diode), the current in fourth quadrant plays a vital role, whereas ideality factor is determined from current in first quadrant. So, I think, ideality factor may not be a significant factor for solar cells.

See these:

https://www.pveducation.org/pvcdrom/ideality-factor

https://www.pveducation.org/pvcdrom/characterisation/measurement-of-ideality-factor

Thanks you Dr Ghosh and Dr Kouhpanji for your answer but my question is somewhat specific . I am talking about ferroelectric photovoltaic devices which are not like p-n junction but showing bulk photovoltaic effect.like BiFeO3 based devices.

The ideality factor n is one of the diode I-V characteristics parameters. It is an indicator of the recombination mechanisms ruling inside the diode. If the recombination occurs in the neutral regions of the diode n=1. and if the recombination in the space charge region dominates, n=2. For diodes whose recombination at the hetero face is dominant n can be higher than 2. The ideality factor affects the fill factor of the solar cell and it is so the as n increases the fill factor decreases.

Mathematically the dark current of the solar cell= Id= Is exp V/nVt , with Vt is the thermal voltage.

For other solar cells irrespective of their structure or theory of operation if their i-v Curve can be be curve fitted by an equation like the above one, then one can equivalently assign an ideality factor of them.

Other wise, it is not necessary to describe the I-V curve with with an equation like that given above and therefore no need to define an ideality factor for them.

Best wishes

Thank you very much Prof. Zekry for giving your time to reply me.

Is same logic applicable to BiFeO3 based ferroelectric photovoltaic devices which shows PV effect but are not p-n junction type.

Dear Chandra,

welcome,

The ferroelectric solar cells are non junction solar cells where they are based on feroelectric effect to build a permanent separating electric field for the photo generated electron hole paper. So, it behaves as resistor in addition to a back electromotive force. It conducts current when the applied voltage is greater than the built in voltage. If the voltage is smaller than the built in voltage the current is ideally zero.

On illuminating the ferroelectric solar cells the generated electron hole pairs will be separated and accumulated on the poles of the material where the electrons will be collected by positive pole and the holes will be accumulated on the negative pole. The accumulation process continue till a balance occurs between the collection process and the reverse diffusive process leading to the recombination of some generated electron hole pairs.

So, it is expected that the I-V characteristics will not follow the well known diode equation as explained in the first post.

So, there is no sense to speak about the ideality factor as the ideality factor is a parameter of the pn or heterojunctions.

Also there is no need to define an ideality factor for a solar cell since the parameters of a solar cell are:

The short circuit current,

the open circuit voltage.

the fill factor,

The conversion effciency

For more information please follow the link:Conference Paper Formation of solar cells based on Ba0.5 Sr0.5 TiO3 (BST) fer...

Thank you very much Prof. Zekry for giving your time to reply me. Can we propose a model for it. I am interested to collabarate with you. I will provide you experimental I-V data .

Dear Chandra,

Sure you are welcome. You are a very active young scientist and you will make great achievements.

Best wishes

A good compact definition is given here

https://pveducation.org/pvcdrom/ideality-factor

Here are some publications for the same

On the Uniqueness of Ideality Factor and Voltage Exponent of Perovskite-Based Solar Cells, Sumanshu Agarwal

J. Phys. Chem. Lett., 2014, 5 (23), pp 4115–4121

DOI: 10.1021/jz5021636

Accuracy of expressions for the fill factor of a solar cell in terms of open-circuit voltage and ideality factor

Journal of Applied Physics 120, 123111 (2016);

https://doi.org/10.1063/1.4962511

Understanding the current-voltage characteristics of industrial crystalline silicon solar cells by considering inhomogeneous current distributions

O. BREITENSTEIN

OPTO−ELECTRONICS REVIEW 21(3), 259–282

http://www-old.mpi-halle.mpg.de/mpi/publi/pdf/11299_13.pdf

A comparison of the effect of CdCl2 and MgCl2 processing on the transport properties of n-CdS/p-CdTe solar cells and a simple approach to determine their back contact barrier height, H. Bayhan

http://livrepository.liverpool.ac.uk/3004558/1/HB-manuscript-kd_JM-HB2.docx

Although it is not completely relevant, I was hoping that this might be useful as the paper discusses on similar lines that your reached is focused with. https://www.epj-pv.org/articles/epjpv/pdf/2014/01/pv140011.pdf

Dear Dr. Zekry,

I have a general question: from the standard I-V curve equation I = I_L - I_0 (exp(qV/nkT) -1), one would find, for the same I_0, a large n seems to give a smaller forward current, thus, a large V_oc, and higher efficiency. How to explain this?

Regards,

Yong

hai every one,

regarding ideality factor of solar modeling i have one dought,

how can we find ideality factor value, using mathematical model. because every diode has some ideality factor, but how to find that ideality factor,

thank you sir's,

Hello,

The ideality factor and the series resistance for well-behaved diodes can be determined from the slope and intercept of the I*dV/dI versus I graph. By well behaved diodes, I mean those whose IV characteristics can be expressed as I = Io*(exp((V-IR)/nVT)-1).

Dubravko

Any reference papers for finding Idealty Factor?