This pic shows the J–V characteristics of my solar cells under illumination. this is normal or anormal?( i see in articles the curvature of the chart is downward but for me It is as follows.no problem? and in table why is the fill factore unordered while PCE%indicate a normal incremental value?
Dear Fatimeh,
You solar cells have a very large nonlinear series resistance and therefore they show an s-curve i-v characteristics demonstrating such type of non properly operating solar cells.
I would advise you to extend the measurement of the i-v curves at larger forward bias voltage to see when the cell conducts current appreciably in forward bias.
Your solar cell parameters are very far being operating as an ordinary solar cell. So, you have to reduce much its series resistance.
Best wishes
Dear Fatimeh,
You solar cells have a very large nonlinear series resistance and therefore they show an s-curve i-v characteristics demonstrating such type of non properly operating solar cells.
I would advise you to extend the measurement of the i-v curves at larger forward bias voltage to see when the cell conducts current appreciably in forward bias.
Your solar cell parameters are very far being operating as an ordinary solar cell. So, you have to reduce much its series resistance.
Best wishes
Dear Fatemeh,
I'm sorry to say so, but your current--voltage characteristics are highly anomalous. For such kinds of curves it doesn't even make sense to calculate the fill factor.
What material are your devices made of? Do you also have current--voltage measurements performed in the dark?
Dear Jan-Martin Wagner
The I–V curves have been recorded by connecting the cell to an external variable resistor and by measuring the current flowing through the resistor and the corresponding voltage across the resistor
Sorry, I meant it differently: Dor you have additional information about the behavior of your devices in the dark?
no. I dont have current--voltage measurements performed in the dark.
Would it be possible for you to make such a measurement in the dark? Because if so, this would most likely give very helpful insight. (On the other hand, this only works if your devices have sufficient majority-carrier conductivity in the dark, of course.)
How can i measure in the dark؟ what is method? or how can i measureconductivity in the dark?. We measurement the electrical conductivity was measured at room temperature.
we determine Conductivity of the samples by using four-probe technique as tablets (bulk no film) . how can i neasurement conductivity in the dark with the above device؟
This is easy: Just measure the J–V characteristics of your solar cells with the illumination switched off (both in the set-up and in the lab), and have some shading elements put over the sunny side of your cells to block the residual light; then you are in a "nearly dark" condition. For "full darkness", put your whole measurement seet-up in a box where no light can enter.
Room temperature is OK, of course. One more hint: If possible, do measurements of the J–V characteristics under illumination for several illumination strengths; this can reveal nonlinearities possibly present in your solar cells.
The idea behind is this: What you measure in the dark is an inevitable loss (because under illumination, the solar cell itself produces a voltage which is able to drive this current). However, for some solar cells there are additional loss mechanisms that only become active under illumination, and which might vary with the strength of the illumination (e.g. due to an injection-dependent lifetime of excited carriers).
Yea, those are not very good solar cells. Probably one of the interfaces between layers in your cell is blocking current (like a Schottky contact) - that produces the "nonlinear series resistance" Prof. Zekry mentioned, and leads to the weird shape.
My best recommendation is to fabricate test structures where you can measure IV curves of the different interfaces in your cell separately - that way you might be able to find out which one is the problem.
Dear Fatemeh,
welcome,
As my colleagues above noted, the dark current is essential to explain the behavior of the solar cell. In order to measure it using a voltage source an ammeter and voltmeter in addition to a series resistance with the diode to limit the current in the solar cell. You need to measure the solar cell in the forward and backward biasing.
I expect that your cell shows a diode characteristics with a a built in high nonlinear series resistance in the cell because of the nonideal interfaces between the metals and the transport layers.
To measure the device characteristics please refer to the work: Article A distributed SPICE-model of a solar cell
Best wishes
Dear Fatema,
please make sure that the values of FF and efficiency are in %. Is it 0.25% or 0.25 = 25%?
Apart of the quality of the solar cell, you should make sure you measure correct. Dark curve like Martin advised is essential. Calculate Rs, Rp as Dr. Zekri hinted to know more about your losses quantitatively.
Your Voc is high. Good news.
Good luck
Dear Fatema,
Can you please give us a briefly information about the cell that you made such as the photo active layer structure ETL and HTL layer . As it seems there is an issue in the active layer ?
Regards,
A photo diode can do This. First we have to calibrate the system with the used load line. Second we start to take voltage measurement. The photo diode current can be in to BJT. The BJT is used as a current to voltage converter. This way we can relate intensity to voltage reading.
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