Dear/ colleagues,
My glove box is currently having some issues that don't guarantee an inert atmosphere during the fabrication of my organic solar cells. However, I could get a PCE of 2.4% , with glove box having the current issues, for device with inverted structure as follows:
ITO/ZnO/P3HT: PC70BM/MoO3/Ag.
My question is, shall the PCE of the device increase if the glove box is working properly? (Assuming all other parameters are fixed).
Please note that:
1- Only the active layer is spin coated inside the glove box anyway and I have to take the substrates outside the glove box for evaporation of MoO3 and Ag.
2- The device is measured outside the glove box, but immediately after the deposition of Ag electrode.
I'd be grateful if you can advise me and share your experience.
Best regards,
Michael
Dear Michael,
The moisture levels in a glove box definitely affect the performance of your organic solar cells. This had been proved in the early development of organic solar cells.
You mentioned that your solar cells were measured outside the glovebox. I believe it is in the air without the encapsulation of your devices. This is another problem. Ideally you should get your devices either to put into a sealed sample chamber or encapsulated. This can reduce your device degradation during your measurements.
Finally, the efficiency of organic solar cells also depends on other factors such as relative thickness of each layer, the interface between two layers, anealing temperatures and etc.
According to the current performance of your devices, you could get much better results if you have had controlled fabrication and testing environments.
Hope it helps
Best wishes
Xuhua
Dear@Michael,
welcome!
I will not repeat what has been said by the colleague Xuhua Wang .
I would propose that you compare your results with those published in the literature for the same structure and produced under protective atmosphere.
You can also see in the literature how far the exposition to the normal air during the fabrication can detract the performance.
May be the period of transporting the the active material while transporting to the evaporator is most critical period for exposition to oxygen and moisture.
Otherwise you solar cell is naturally sealed by oxide layers if there are no pinholes in the structure.
You can also try to follow the if any further fall in the efficiency by further exposition to air.
You may follow the paper in the link: Article Degradation Patterns in Water and Oxygen of an Inverted Poly...
Best wishes
Dear Michael,
A few points to consider:
(1) Have you tried depositing the P3HT:PC70BM layer in air? Comparing the results for samples deposited in air vs samples fabricated in your glove box would give you an idea on the air sensitivity.
(2) Do you do solvent annealing of the films? for P3HT:PC70BM, slow drying of the films in a closed petri dish helps. We usually keep one film per petri dish.
(3) Do you know what is the thickness of your active layer? On Pedot (4083), we've found 220 nm ish to be the best. This may change based on any spacer effects due to ZnO and MoO3.
(4) The ZnO if it is processed from sol-gel can be sensitive to ambient humidity levels. It may need optimisation.
(5) The MoO3 deposition rate can also influence the performance. Typically slo rates are best (0.1 - 0.2 Angstroms/sec). The thickness of MoO3 should also be carefully optimised.
I don't think that measuring outside results in a rapid decay of performance. We often measure our cells in air without encapsulation including EQE, so it's most likely the problem lies with the above conditions or your glove box.
Hope this helps!
Dear Xuhua Wang
Thanks a million for your response,
Yes, my devices are not encapsulated. Do you think they degrade that fast? As the J-V characterization is performed within few minutes after electrode deposition. I'm currently working on my glove box and hopefully it will make the results better. I'll let you know future updates.
Best regards,
Michael
Dear prof. Abdelhalim abdelnaby Zekry
Thanks a lot for your answer and suggestions. Actually, my results are still lower than those in literature for devices with the same structure, especially for short circuit current density.
Transfer time from the glovebox is also a good point to consider, I'll try to design a sealed chamber for this purpose. I'll let you know the updates in the future. Thanks so much for being always supportive.
Best regards,
Michael
Dear Imalka Jayawardena
Thanks for all your suggestions. I already did the optimization for ZnO and MoO3 and I use approximately a deposition rate of 0.2 A/sec for MoO3. The thickness of the active layer is nearly 100 nm. Meanwhile, I'll give more attention to the first and second suggestions. I'll let you know the future updates.
Best regards,
Michael
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