Hello there,
I just recently started characterizing DSSC solar cells and have purchased a Keithley 2400 SMU, from university project funding. Unfortunately I still cannot figure out how to measure I-V characteristics. The multi meter shows a DC voltage of ~0.2V being generated. The voltage and current measurements should be the same when measured with the help of 2400 SMU, which is not the case. Do I need to alter the settings of the SMU in order to get the (precise) measurements.... is it something related to the compliance settings... please suggest. Am using a two wire arrangement to manually measure current and voltages. Think the same thing is also messing up my automated I-V curve measurements, preformed using SMU and I-V software.
Attaching images of the SMU and Multi-meter readings.
Would be really thankful for the help in this regard. Thanks
In order to measure I-V characteristics you need precise and adjustable (stabilized) power source and perhaps a series of current detectors (especially is you want to cover several orders of magnitude). Measurement of very low currents may need special arrangement.
Hi! Do you have a good manual? You can download one from http://research.physics.illinois.edu/bezryadin/labprotocol/Keithley2400Manual.pdf
and on page 3-18 and onwards it seems you might find some helpful information.
Hi Mike,
I was also facing the same problem... First you test Keithley 2400 for know resister, measure I-V characteristics, by simply connecting resistor to the two ends of Keithley input. Press 'V' key of front penal in the 'Source' column, edit some voltage (say 1V) and by double pressing same edit button you move to compliance, set that compliance to mA or A. Press on button after these settings and now press ON button it will show some current value. Repeat this for other voltages and measured current. Plot the data points. if you get correct resistance value from that slope then it means that your SMU is in well condition. It is also advisable that Keithley meter connect through stabiliser. If you are familiar with front panel key, set start voltage & stop voltage in a particular step for particular delay time for same resister and set compliance to ~mA. If you are not familiar with those key then you have to follow Keithley Manual. This is the way first you test your SMU is working properly or not. Then you can try for diode or other resisters as well. Better you go through Computer interfacing, it will be easy for plotting and the extraction of data.
In my case SMU unit didn't work properly, it got damage because of not connecting through stabiliser and earthing issue. Now we had resolve those problem properly.
I Hope that , this will convince you.
A Source Meter Unit (SMU) either sources a voltage and measures a current or sources a current and measure a voltage. You are sourcing a voltage (Vsrc=0V) and measuring that same voltage which the system is trying to keep as close to zero as possible. If you change the "meas" from V to I (current) and increase the Cmpl current to about 0.5A you will read the short-circuit current of your cell.
What you are seeing with the multimeter instead should be something very close to the open-circuit voltage (Voc) of the cell because the resistance across the multimeter in voltmeter mode is very high (>1MOhm) however 0.2V seems a bit too low for a good DSSC.
Usually the Voc of a solar cell is obtained by measuring the current at different values of the voltage applied. The Voc is the voltage corresponding to I=0 Amp which you can calculate by interpolating the curve around zero current.
Also remember to set a decent value for the compliance current (at least higher than the short-circuit current of you device).
You might be able to obtain the Voc also by sourcing zero current Isrc=0A and measuring the correspondent voltage but I am not 100% sure about this.
Oh my god.. You have changed the compliance level to 105 micro Ampere. Please change it to 0.1A.
To measure I-V by SMU for emerging PV (DSSC/OPV/PSC), you will be find some information from this project,
https://www.researchgate.net/project/Performance-rating-measurement-of-emerging-PV-for-Outdoor-AM15G-and-Indoor-lighting
For your reference !
thank you !
Mickey
Hu,
You have changed the compliance level to 105 microAmpere. Please change it to 0.1 A. Have you corrected the setup. Please inform me once after correcting.
Dear Colleagues,
I came late to this question but my answer may be useful for answering such basic question. I would recommend the answer of Mr. Bausi, it is technically obvious. and conceptually clear.
The most important point here for such an instrument its acts as an active load or as from the name of the instrument as source. There are two sources either current source and voltage source. So the instrument can be used either a voltage source or a current source where it measures the voltage between its terminals in case of current source and in case of a voltage source it measures the current flowing through it.
THE MAJOR POINT HERE WHAT IS THE SUITABLE SOURCE FOR MEASURING THE SOLAR CELL IN ITS THIRD QUADRANT OPERATION?
You have to choose here the voltage source mode with the positive terminal connected to the anode of the solar cell and negative terminal connected to the cathode. Then we change the voltage source from zero voltage at the short circuit condition where the we will measure the short circuit current up to V=Voc the open circuit voltage where the current will tend to zero.
Best wishes
You Will need to sweep the voltage (select source voltage) at certain selected/desired range. E.g. select from -1V to 1V @ step size of 50mV (having smaller step size will provide precise accurate and large data set). As voltage is is change there will be change in the current. So you need to collect data corresponding to applied voltage and measured current. Yes as mentioned by other please alter the voltage compliance.
Alternatively, you can use certain software (Agilent, keysight, Lab view) and interface the instrument with computer to control instrument, select variable and log data accordingly. If you have Agilent/keysight program available with you, let me know i can help you with the programming.
All the best!
Kind Regards,
Krishna Nama
Well I just like to add that there is a small button front/rear on the bottom right corner that switches between the front banana connectors to the back ones. Also it is important to use 4w (four probe measurements) since solar cells have very low series resistances.
Adding a little bit different, but similar problem, I am having trouble in stabilizing measured voltage (read on the display of Keithley 2400 SMU) of a two-cell open circuit (using source 0.0A; one cell with 0.1 M KCl and the other with a solution with certain amount of an ion). Measured voltage goes down slowly at random, making it dificult to get a calibration curve. Sometimes, with the same sample, voltage goes down to a minimun and then goes up. I am using front panel with 4 probe mesurement (two dual banana connectors). Does anyone know how to solve this variation, how to get stable measured voltage?
@Frederico Barbosa de Sousa- Please elaborate your question. I think I can help you. Can you message me on research gate describing your problems?
Avishek Das Hi, I'm wondering if you have any advice for a strange inconvenience regarding the 2400 device. I am using LabVIEW to set the voltage but apparently we must hit the 'Local' button in order for the voltmeter to display the changing current value and from what my labmates say, it affects the readings, as well. I plan on doing a bit of experimentation to see if I can figure out what's going on here but maybe you have some advice before I put any unnecessary time into this? Thanks!
(@ Suzanne Rosenzweig)
Please message me on my research gate profile and elaborate your question. Which version of LabVIEW are you using? I can't understand your question. Please send some pics of the display and elaborate your question.
I think I can help you.
Frederico Barbosa de Sousa Avishek Das , what is the solution for your problem because I am also facing the same problem . My current values are not stable when I am measuring , it for a KCl electrochemical cell.
@Aayushi Please message me on my research gate account and state your problem. I will try to sort out as soon as possible. If possible send me your connection diagram.
Dear Aayushi Arya
I identified two problems: (1) my BNC-banana connector was not working, then I replaced; (2) I was mistakingly using 4-wire sense, then I changed to 2-wire sense. I recommend to makea test using a 1.5 V battery to check if your SMU is able to measure the expected voltage. This helped me a lot.
Avishek Das I have sent you a message regarding I-V through Labview software.
If the compliance is reached, it starts blinking. In your case, the voltage is probably not measured, because you apply AND measure voltage at the same time. It means, if you apply 0V, it is fully correct that you measure 0.0001 V (which is almost zero). I suggest to apply 0V and measure current (which would be the short-circuit current of the solar cell) or you use Isource and apply 0A and measure the voltage of the cell (which would be the open-circuit voltage). Applying 0A means that the SMU will ramp up to a voltage that suppresses any current flow. Thus: Isource 0A results in using the SMU as voltmeter.
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