I'm working with my I-V graphs of a CdS/PbS solar cell , and I was able to determine the values of the VOC and ISC , but how I can understand these parameters in terms of the functioning particularly of a solar cell ?.
and, is there and expression for these parameters as a function of the carrier concentration, density of states, etc. ? for a p-n junction solar cell.
Hope someone can help me with this
:)
Hope that the following resources are useful for you. I recommend starting with the first one as it uses animations and also oriented to the physical nature of the solar-PV cell performance.
http://pveducation.org/
Chapter 10 in,
Book Dynamic Security of Interconnected Electric Power Systems - ...
and
Conference Paper Experimental Analysis of Conditions Based Variations of Char...
Dear Franklin,
You requested the full-text of a pre-print, while I already added the approved published version. Please follow,
Conference Paper Experimental Analysis of Conditions Based Variations of Char...
where you will find the full-text.
Textbooks are your best bet, but basically:
The Jsc mainly depends on absorption. If it is low, you may need to improve light absorption.
The Voc mainly depends on recombination. If it's low, you have a lot of recombination sites and you should try to passivate these defects.
Also, Voc is a function of ln(Jsc), so if one is bad it can impact the other and vice versa.
Dear Dr. Manuel,
Thank you for your feedback. You wrote "Voc is a function of ln(Jsc), so if one is bad it can impact the other and vice versa". May I ask you to elaborate this point from physical and/or mathematical modelling points of view?
You can follow this discussion
https://www.researchgate.net/post/How_does_the_open_circuit_voltage_of_a_photovaltaic_device_change_with_intensity_of_incident_light
Hi Franklin,
Following Q-A may help you:
https://www.researchgate.net/post/Why_my_planar_P-I-N_junction_perovskite_solar_cell_exhibit_low_Voc_but_high_Jsc
In order to understand the operation of the pn junction solar cells you need to study the pn junction diode under dark condition, which is like the operation of the rectifier the diode except it is built for solar cell operation. In addition to the dark characteristics one has to study the illuminated characteristics of the solar cells with the cell short circuited. By superposing the two cases, one get the the characteristics of the illuminated characteristics of the solar cell under any working condition.
It is so that the cell current I can be expressed by
I= Isc - Id,
Isc is the short circuit photo current,
Id is the dark current which can be expressed by:
Id= Is( exp V/nVt -1),
Is is the reverse saturation current and n is the ideality factor of the diode while Vt is the temperature equivalent voltage.
Here it is assumed that the cell current measured out of the anode and the the cell is assumed forward biased. Also the series resistance and the shunt resistances are neglected.
As Is
Voc, Isc, "how I can understand these parameters in terms of the functioning particularly of a solar cell ?"
That's a very nice question. I'd say, Isc stands for all the generated charge carriers that contribute to the current, hence strongly depends on the optical and electrical properties of the solar cell materials.
Voc, however, measures the maximum potential energy that could be delivered to a load. It is given by the offset from the dark conditions. For example, cooling your device will decrease the dark current and hence increase the Voc under sunlight. As no energy is extracted from the solar cell at open-circuit, all the energy must get radiated back (to sun). The more gets send back, the higher the Voc. Therefore, the Voc degrades with the presence of non-radiative recommbination centres, because the generated charge-carriers under sunlight would recombine without the emission of a photon.
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