I'm optimizing the procedure for making inverted PSCs: ITO / PTAA(8nm) / CsMAFA(320nm) / PCBM(60nm) / BCP(9nm) / Ag(100nm).
The cells look very good, I have a very good FF (0.70) and Voc (1.0V), but the Jsc is very low (15 mA/cm2). The active area is 0.2cm2 and light intensity is of 1sun.
Does someone know what is making the current so low and what should I do to increase it?
Thank you very much!
What is the energy gap of your perovskite?
I think the most factor affecting the shortcircuit current is the presence of many defects that can act as an effective recombination centers. This may be in the volume of the perovskite and it may be in the interfaces with the transport layers
You can measure the carrier life time by the decay rate of the open circuit voltage.
The other factor is that the thickness of the material is not sufficient to absorb the incident solar radiation. So, you can increase the thickness of the material and see its effects on the PCE.
I think the most serious factor is the degree of the crystallinity of the active layer.
You have to see for methods to increase the crystallinity.
You can also try to passivate the interfaces to reduce their recombination rate.
I think you have to plan investigation experiments to systematically optimize your structure.
For the using the open circuit method to measure the lifetime of solar cells please see the paper in the link: Article A. Zekry and G. El-Dllal, “ effect of MS contact on the elec...
Best wishes
Article Enhanced short-circuit current density of perovskite solar c...
https://www.researchgate.net/publication/343309569_214_efficiency_of_perovskite_solar_cells_using_BMImI_additive_in_the_lead_iodide_precursor_based_on_carbon_nanotubesTiO2_electron_transfer_layer?_sg%5B0%5D=9EiU2CcG8WJs0MR-eZzNR3B_hCJ-A4K6TaUmrTe3twY8_WF1zyml1ur3lbliasifMjbiTmBAwcGJRPWayAeac1l8VBgb_ryS63pQZXnK.lGqxAwmvxxY1k6LgWdj1SGkbsqT3BqHMu0JbLIWV8GngvrDu2tgI2d5i2Fmc74P5mdO6L2HP4UtfEBfSO8aNlQ
Mustafa K. A. Mohammed, Mohamed Azab , thank you for your suggestions. I understand that by doping the underlying layer of perovskite (ETM for n-i-p and HTM for the p-i-n) the perovskite grains quality can be boosted. However, I tried to dop PTAA with F4-TCNQ and it didn't improve the Jsc.
One can not simply answer Your question. It realy depends on what is wrong with your solar cells. You need to carefully evaluate your preparation procedure.
What is the energy gap of your perovskite?
I think the most factor affecting the shortcircuit current is the presence of many defects that can act as an effective recombination centers. This may be in the volume of the perovskite and it may be in the interfaces with the transport layers
You can measure the carrier life time by the decay rate of the open circuit voltage.
The other factor is that the thickness of the material is not sufficient to absorb the incident solar radiation. So, you can increase the thickness of the material and see its effects on the PCE.
I think the most serious factor is the degree of the crystallinity of the active layer.
You have to see for methods to increase the crystallinity.
You can also try to passivate the interfaces to reduce their recombination rate.
I think you have to plan investigation experiments to systematically optimize your structure.
For the using the open circuit method to measure the lifetime of solar cells please see the paper in the link: Article A. Zekry and G. El-Dllal, “ effect of MS contact on the elec...
Best wishes
The possible reason is very much difficult to guess. I guess the series resistance is high. Try to obtain the Nyquist plot and get a rough idea. Then further strategies can be opted.
Abdelhalim abdelnaby Zekry, thank you for your answer!
Since I’m using the TriCation perovskite, I suppose the band gap is around 1.65eV. Indeed, I used the absorption spectrum to obtain the Tauc plot, and the estimated band gap was around 1.6eV. This band gap is low enough for ensuring a high current generation.
Concerning the crystallinity of the perovskite layer, I understand that the presence of defects would trap charges and result in a current decrease. But if the defect density is high, wouldn’t it also affect the Voc? As said by Ravishankar (DOI: 10.1016/j.joule.2018.02.013), “VOC is controlled by the splitting of quasi-Fermi levels and recombination inside the perovskite, rather than being governed by any internal electric field established by the difference in the charge transport layers work functions.” Also, the perovskite grains can easily be seen in the SEM images I attached, and they seem nice.
About increasing the thickness, I also had that hypothesis. However, increasing the thickness to 460nm (by increasing the concentration of the solution) resulted in a Jsc decrease. But I’ll measure the carrier life time the decay rate of the open circuit voltage, as you mentioned, to have a clearer idea about this.
About the interfaces of perovskite with the charge transport layers, “hysteretic variations can be directly correlated to the nature of the perovskite crystal in contact with the selective layers”( DOI: 10.1016/j.joule.2018.02.013). This means that by hysteresis test I can deduce the quality of the perovskite interfaces. If the PSC has hysteresis, then I can try to passivate the interfaces to reduce their recombination rate. Do you agree?
Thank you for your time.
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