Hi, the PEDOT-PSS dispersed in water not miscible with it in ratios 1.3, 1.5 wt.% when you cooling it and solidifies does not affect the conductivity this solidification because there is water with the polymer you can put it in room temp. and it will return back to the original liquid solution state

hi Husna,

I just remember from my PEDOT:PSS dispersions that they were delivered with a freeze indicator - so the supplier takes care that the dispersion is not cooled down to critical temperatures - as this would affect the performance to my knowledge. In my work I added some alcohols to my solutions - and over time I observed gelation - if this occurred I always had to dispose the dispersions. Do you observe any difference of your solution after heating them up again when you filter it (you should always filter prior coatin/printing)? This could be a hint for undesired changes of your material.

Regards,

Sebastian

@Husna Jan Following the above suggestions, you should be able to use it although there have been some difference between the originally supplied solution and redispersed solution as Ahmed Amir Flaieh suggested. For research purpose, you may not notice significant change such as device fabrications. However, if you compare two solutions and work on the lifetime of your devices, this could affect it greatly.

Thank you for your answers Xuhua Wang , Sebastian Marius Raupp and Ahmed Amer Flayeh .

It is a 1.3 wt % dispersion in water. I have not used this before.

When I kept it at RT I can see agglomerates of PEDOT:PSS at the bottom. If I filter it prior to spin coating won't I loss some of the materials and change the concentration?

Husna Jan the best temperature must be at 5 degree centigrade when you cool it down further the material starts to solidify and this will be treated by heating to room temperature for a while not permanently kept at this degree after solidification melts then get it back to 5-degree centigrade if you see agglomerations you can treat this by sonication but if you used the heat with sonication the water will evaporate affecting the concentrations and you can use the filtration but I don't prefer this one because you lose some weights of the PEDOT-PSS so sonication to redispersed the solution with moderate temperature to overcome the sediments and agglomerations

Dear Husna,

Yes filtering will lead to a certain loss of material. But you could determine the exact concentration afterwards... If I don't filter I always get shorts in my samples. That's why I always filter prior coating or printing. Regards, Sebastian

Can I use 0.45um Nylon filters for the same Sebastian Marius Raupp ?

Dear Husna Jan

I used 0.45 µm polyvinylidene fluoride filters in the following experiments:

- Slot die coated and flexo printed highly efficient SMOLEDs

- An experimental study on the reproducibility of different multilayer OLED materials processed by slot die coating

when casting from water-Ethanol dispersion. For water-1-Propanol mixtures (see Slot die-coated blue SMOLED multilayers) I used the same filter. Nylon might work as well; but PVDF worked fine in our case.

Regards,

Sebastian

All of your suggestions worked for me. Thanks. I have another doubt.

I mixed very small amount of PEG with PEDOT:PSS and then annealing at 70 deg for 24 hrs. But I found that the film has formed but it was wet. Why is that? What are the possible ways to prevent this? Xuhua Wang , Sebastian Marius Raupp , Ahmed Amer Flayeh

Hi Husna,

Is the solvent water or remaining PEG?

Why do you anneal it at 70 deg? Could you increase that or apply vacuum?

Regards

Sebastian

I tried increasing the temperature to even 135 deg and tried applying vaccum as well. But it didn't help.

I was following this paper which mention to anneal at 70deg :

Chinese Science Bulletin 2003 Vol. 48 No. 22 2444-2445 ,Effect of addition of poly- (ethylene glycol) on electrical conductivity of poly(3,4- ethylenedioxythiophene)- poly(styrenesulfonate) hybrid .

Dear Husna Jan,

I don't think 70 degree C is enough to remove water residuals from the PEDOT:PSS films. Normally we did the films was heated up to 120 degree C for half an hour on a hot plate.

Hope it helps

Dear Husna,

can you determine the water content you still have remaining in your samples? How much time is between annealing and measuring the water content? PEDOT:PSS is likely to take up water from the atmosphere relatively fast....

Regards, Sebastian

I think that was excess PEG which I found wetting the film even after annealing. I think the amount of PEG I took was too much and since annealing was done in a closed furnace PEG remained. When I tried on a hot plate at 100 deg just for 20-30 min and reduced the amount, it really helped. Thanks for all your suggestions.

Hi Husna,

Happy to hear that you could solve the problem! I recommend to store your samples under vacuum after annealing if you do not process them further immediately. This was best in my experiments.

Regards

Sebastian

I have another doubt. To make x wt% of any cosolvent in PEDOT: PSS, should I consider the exact mass of PEDOT: PSS (i.e., 0.013*V of PEDOT: PSS), or can I use the wt of water dispersion as such (for example, 2.5ml of PEDOT: PSS dispersion as 2.5g) while calculating the amount of cosolvent required? Sebastian Marius Raupp Xuhua Wang

Hi Husna,

I used to take the mass of pedot:pss and refer to that. For all solvents I recorded the mass to be independent of the temperature etc. (so no volumes measured). If you have any coating solution in the end you could measure the weight of pedot:pss gravimetrically to double check. Regards Sebastian

Thank you for your answer Sebastian Marius Raupp .

I fully agree what Seb suggested. The weight or mass calculation is much controlled to optimise the dopants.

Thank you for the answer Xuhua Wang

Extending this question, I also have one query.

I need to add x.wt% of some additives like Trition-X or EG in PEDOT: PSS (PH1000) dispersion which is 1-1.3 wt% in water. How to calculate it? For instance, if I need to make a solution of 2 ml (total) with 5 wt% of some additive? Your help will be appreciated. Thank you