When measuring dark J-V of solar cells, why is the minimum current voltage measured for the dark I-V characteristics of the OSCs not at zero?
The charge traps happen in your devices due to the device structure design.
Dear Leiping,
Please see the link below
https://ieeexplore.ieee.org/document/7749709
https://pubs.acs.org/doi/10.1021/acsenergylett.0c02599
https://www.nature.com/articles/s41467-020-19434-0
You could find more references using key words search in the Web of Science.
All the best
Xuhua
As a result of the presence of a leakage current, this leads to the emergence of a non-zero deflection voltage and it moves away from zero a lot as the leakage current increases.
Dear Leiping,
"Zero current voltage shift" happens due to capcitance effect existing in the device when charge traps in the active layer. Related work can be seen in Article Photomultiplication Type Broad Response Organic Photodetecto...
Just for curiosity (because this is not my field of expertise): Does that measurement result look the same when you invert the direction of the voltage sweep, or does it look differently when starting either from positive or negative voltages? (If I had to guess, I'd say that in the case you have shown [Picture1.emf], you started from negative voltages. Is that correct?)
As a result of the presence of a leakage current, this leads to the emergence of a non-zero deflection voltage and it moves away from zero a lot as the leakage current increases.
In the dark, no current will be generated by a PV device, and there will also be no voltage produced (only a thermoelectric device may produce power output in the dark). Therefore, when measuring the dark J--V characteristic, the only reasonable value at zero voltage is zero current. A nonzero current at zero voltage cannot be explained by "leakage currents", Ammar Qasem, because a leakage current only flows if there is a voltage applied. Instead, as already mentioned by others, it can only be of capacitive origin -- but this has nothing to do with leakage!
Check https://www.pveducation.org/pvcdrom/characterisation/dark-iv-measurements
Also check https://books.google.co.ug/books?id=UfeSBQAAQBAJ&pg=PA395&lpg=PA395&dq=dakr+J-V+curve+shifted+for+some+devices?&source=bl&ots=950XIYt5hr&sig=ACfU3U3VOvavhswHWcwX7bDNrpDPWJTd4g&hl=en&sa=X&ved=2ahUKEwjTq6fu9aTwAhXhAmMBHTnaB_cQ6AEwDXoECBYQAg
Hello Juan, you can use this paper to know the problem
https://www.allaboutcircuits.com/technical-articles/interpreting-current-voltage-curves-of-different-materials/
I couldn't open the Picture 1 .emf iile Could you send it out as a .pdf or a .jpeg file? The behavior suggests that there is a problem with ther measurement system. I agree with Jan-Martin.
Dear Alan L. Fahrenbruch, at first I also couldn't see the image in that file, but putting it into a blank Word page (via the "insert from file" option) made it visible. Another option is to use the most simple graphics program "Paint" to open this file. It is a logarithmic current--voltage plot, with the sharp dip that indicates zero current occurring at some positive voltage (about 0.25 V).
The main cause of shifting is the asymmetries arise due to the native defects at material-electrodes interfaces.
In my opinion, the kiink is most likely due to a problem with the measurement circuit. Measurement as a function of time (e.g., J(t) vs time at V < V,kink) and at V > V,kink) should reveal the cause.
Could it be that your "dark" measurement is actually not fully dark, but only at very very low light? That would also explain your observed curve shape. If I remember well, OSC (= organic solar cells?) are working very well at low light. This means, even at very low light, a voltage can be measured.
The other explanation, as mentioned by others: capacitive effects/sweep speed.
I agree with Jan Haschke (...not fully dark...). My answer above (..kink...) was for a different question.
Long lived trapped charge historicist? Charge storage in various depletion regions and/or capacitance effects (again charge storage causing voltage offsets) in wires and extraneous junctions perhaps external to the solar cell? Good to see your still active and making a significant contribution as always!
Dear Leiping Duan ,
Hope you are well!
You display logI versus V.
If you have complete darkness, then the current must be zero at zero voltage for solid sate solar cells for static I-V characteristics where you measure the by DC instruments while applying DC voltage.
What is the problem in your figure?
If you have log current scale you will never get a zero because log 0= - infinity.
And this what you have in your figure.
In order to show the zero point as a zero value you have to choose a linear plot not a semilogarithmic plot as you did here.
Best wishes
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