I am trying to fabricate p3ht:pcbm solar cells to obtain a reference efficiency for my future research. However, my photocurrents have been extremely low. From what I've read, ITO cleaning procedures are absolutely vital to making these devices work. I was wondering if ultrasonication in acetone, alcohol, DI water for 10-15 minutes each would be sufficient to produce a good PEDOT:PSS layer? Also, I've noticed my ITO is extremely hydrophobic. Is there a better cleaning method that is fairly universal?
Hello
Two things:
- Cleaning PEDOT:PSS in Ultrasonication is not a good idea. Since it dissolves in water it can just peal off. If it worked out for you please share the protocol.
Cleaning only the ITO with UV-Ozone, is the easiest way to remove carbon and thiol contaminations.
- Treating the ITO with plasma will change the surface properties and make it hydrophilic. It will improve the PEDOT layer formation. Also, plasma treatment will change the ITO surface workfunction and make it a better hole injector. This is one of the reason why it is so important to use plasma on ITO.
Check this article: http://scitation.aip.org/content/aip/journal/jap/87/1/10.1063/1.371859.
Have a nice day
Thanks, Omri! Sorry about the confusion - I only ultrasonicate the ITO coated substrate.
If plasma treatment make the surface more hydrophilic then why do some papers report using higher ratios of solvent to PEDOT:PSS? I've seen alcohols to PEDOT"PSS in a 5:1 (v:v)
I do not know. Can you attach the papers?
The pedot:pss can be dissolved in water as well.
If you wait with the ITO by leaving it in water or ethanol, the ITO can be hydrolyzed and become again hydrophobic.
You can just try it out, take a small piece of ITO coated substrate, put a drop of water over it, Dry it and give it an ozone treatment and put another drop of water on it,
You should be able to see the change.
It does not matter what solvent you will use for the PEDOT (you would still get a conducive layer). you can use ethanol which will speed up your drying of the PEDOT layer. I think that the ratio will determine your layer thickness as well.
Which one is better, Plasma cleaning of ITO coated glass substrates or UV/Ozone curing?. Usually, we clean the ITO substrates with AMD (Acetone, Methanol, Distilled Water, 5 min each), followed by UV/Ozone curing for ~ 20 min. My Jsc is very low as similar to what Nicole Dillard says. Please suggest best cleaning procedure for better results.
Nicole...The cleaning procedure that I use is Ultrasonication for 20 mins each in sodium dodecyl sufate solution in DI water, DI water, Acetone and 2-Propanol....It is required to plasma clean or UV ozone treat the samples to make it hydrophilic,....I am not sure about alcohols in PEDOT:PSS...generally I have seen such a mixture used when PEDOT is coated on top of active layer....You can pre anneal the ITO and then check if it becomes hydrophilic....Not sure about that though.
How effective is the RCA-1 and RCA-2 cleaning of ITO substrates followed by O2 plasma treatment? Won't there be any improvement in hydrophilicity?
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