My current structure is based on ITO/SnO2/Perovskite/Spiro/Ag. The samples could reach a Voc=0.95V, Jsc=18mA/cm2, FF=60%. How could I find out what is the most serious problems with my devices? Is there a way to technically characterize if any layer inside has a problem and requires further improvement? Thanks a lot!
Hello, one of the most serious problems in this configuration is the proper oxidation of Spiro - Ometad . You should try to find optimum time for oxidation ( best way is via absorption spectra) , also molar ratio of dopants is crucial ( LiTFSi , tBP). It is recommended to use Au as anode in normal structure due to favourable work function for better carrier extraction from Spiro. Finally four point probe is a good way to check conductivity of SnO2 and by making hole-electron only devices , it can be observed from TPC (transient photocurrent) which selective layer is still unoptimized.
Dear Jinze Cai ,
If you could determine all the five parameters of the single junction model you can diagnose the performance of the different layers.
So, you need also to determine the Iph, the reverse saturation current, the ideality factor, the shunt resistance and the series resistance.
I observe that your fill factor is too low. This may be due to too high series resistance or too low shunt resistance of both together. Also your Isc is too low if your insolation is AM1.5.
Systematically:
you need to increase the conductivity of the HTL and ETL layers. Specially the spiro ome tad.
You have to avoid the formation of any pinholes.
You have to make the layers as homogeneous as possible.
It is advisable that you optimize every layer by its own by depositing these layers on gals and inspecting it by the microscope and electrically by measuring its conductivity by the 4 point probe. You can also measure its thickness.
Avery effective method in testing the quality of the perovskite is measuring the minority carrier lifetime.
I notice that the researchers neglect this characterization method.
You can measure such minority carrier lifetime by the the method of open circuit voltage decay.
I would like that you follow the characterization method bin the papers:
Article A distributed SPICE-model of a solar cell
and the paper
Article A. Zekry and G. El-Dllal, “ effect of MS contact on the elec...
These two papers will help you make full characterization of your solar cells
in addition to the tips which I gave here.
If you display your illuminated I-V curves I could give you more tips.
Best wishes
Dear Abdelhalim abdelnaby Zekry
Thanks a lot for these detailed analyses and suggestions! Attached is the best IV curve I could get at present.
At present, I do suspect the Spiro layer has some problems. For one thing, if I find out there is a pin-hole issue for any layer, what is the best way to avoid the problem? By changing the concentration or the spin-rate, or other parameters?
For another thing, if I found the surface resistance of a layer (let's say the spiro layer) is extremely high, what should I tune to solve this problem (the recipe of Spiro and additives are standard from papers I think)?
Thanks again for your patience and help!
Dear Jinze Cai ,
welcome again!
From the shape of your I-V curve, the series resistance of your cell is too large!
So, you major effort must be directed to reduce the series resistance by improving the transport layers.
But there is one point to mention.
If you also display your dark current I-V curve together with the illuminated one may see other effects such as the recombination inside the i-region.
To see the effect and how it can reduce the collected photocurrent with the forward bias of the cell. It can also show such shape of the I-V curve.
If this is the case then one must improve the quality of the perovskite material.
Conference Paper Generic Analytical Models for Organic and Perovskite Solar Cells
Best wishes
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