what the parameters should i get from the LCR meter and what equation should to be used for impedance spectroscopy measurements a solar cell
Dear Mostafa,
Adding to Tonny, irrespective of the lcr meter you use you have to firstly bias you solar cell at certain operating point. Then you measure the impedance of the solar cell at variable frequencies starting from low frequency to the highest frequency required. You get the impedance in real part R and imaginary part X. YOU HAVE TO KEEP IN MIND THAT YOU MEASURE SMALL SIGNAL IMPEDANCE SO YOUR AC VOLTAGE MUST BE MUCH SMALLER THAN THE dc voltage and your ac current must be much smaller than the Dc current. The resulting impedance curve is in form of Half circle.
If the cell area is large then the impedance will be low and you to take this into consideration.
For more information please follow the paper:https://www.researchgate.net/publication/3062547_A_distributed_SPICE-model_of_a_solar_cell
wish you success
Article A distributed SPICE-model of a solar cell
May I ask what sort of solar cell you want to measure? The meter you mention only goes down to 4 Hz, which is not enough for a DSSC. You will need at least 0.01 Hz for most cells of that type.
Dear Mostafa,
Adding to Tonny, irrespective of the lcr meter you use you have to firstly bias you solar cell at certain operating point. Then you measure the impedance of the solar cell at variable frequencies starting from low frequency to the highest frequency required. You get the impedance in real part R and imaginary part X. YOU HAVE TO KEEP IN MIND THAT YOU MEASURE SMALL SIGNAL IMPEDANCE SO YOUR AC VOLTAGE MUST BE MUCH SMALLER THAN THE dc voltage and your ac current must be much smaller than the Dc current. The resulting impedance curve is in form of Half circle.
If the cell area is large then the impedance will be low and you to take this into consideration.
For more information please follow the paper:https://www.researchgate.net/publication/3062547_A_distributed_SPICE-model_of_a_solar_cell
wish you success
Article A distributed SPICE-model of a solar cell
thanks a lot Dr.Tony Maine, i want to use it for a quantum dot sensitized solar cell (QDSSC) , is it still also not enough?
thanks a lot Prof.A.Zekry for your explanation. i already have two units one for DC Voltage bias and the other one for DC current bias but i do not know how to use them for impedance spectroscopy measurements a solar cell.
And what you mean with "YOUR AC VOLTAGE MUST BE MUCH SMALLER THAN THE dc voltage and your ac current must be much smaller than the Dc current"?
Dear Mostafa, you are welcome,
You have to develop a test circuit for the impedance measurements for the solar cell where the solar cell is biased at certain operating point and subjected to the bridge.
I will give you some hint. Connect the DC power supply in series with large choke to the solar cell to bias it with DC. Then connect the solar cell from the other side to the bridge via a a large coupling capacitor. In this way you biased the solar cell and separated the DC branch from the ac branch.
It is so that the coupling capacitor C must be much greater than the expected solar cell capacitor. On the other side the the minimum value of the inductor must be such that its reactance must be much greater than the reactance of the solar cell.
The ac voltage applied on the solar cell must be much smaller than its DC voltage, say in the order of tens of milli volt for the small signal condition to prevail.
You must make compromise between the accuracy of the measurement and the validity of the small signal condition. Accuracy of the measurements requires to increase the excitation of the bridge while the small signal requires the decrease of the excitation. So, one has to compromise this. A good sign of that is that both the voltage and current remain sinusoidal with negligible distortion.
wish you success
I suggest you to find and use a potentiostat with EIS module/capability.
http://www.gamry.com/application-notes/physechem/dye-solar-cells-impedance-measurements/
Look for Photovoltaics at http://www.ecochemie.nl/Applications/
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