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I am doing a science fair project on OLEDs. I am testing whether polypyrrole can be used as an emissive layer in a 2-layer OLED. The polypyrrole I am synthesizing is water soluble, and will be spin-coated onto ITO-coated glass substrate. I also need to spin-coat on a hole-injection layer (PEDOT:PSS). I can only seem to find it in what I believe to be water-dispersed form. This will cause obvious problems since both substances are water-soluble. I read on some informal message board that I could drop droplets of water-dispersed PEDOT:PSS into a hot organic solvent with a boiling point higher than water, boil off the water, and be left with organic-solvent dispersed PEDOT:PSS. That makes sense, I am just confused about what organic solvent to use. I believe it needs to have the properties of not dissolving the PEDOT:PSS, ITO, or the polypyrrole, and allow the PEDOT:PSS to become dispersed.

Here is a link to the PEDOT:PSS I am looking at:

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Even if you switch to an organic solvent, if the polypyrrole is in water, it will perturb the PEDOT:PSS layer.

Your best bet would be to use a poly-alkyl pyrrole or other conjugated polymer that's soluble in something that doesn't dissolve PEDOT:PSS.

Let's say you switch the solvent to DMF or DMSO and it dissolves the PEDOT:PSS. Then you spin-coat that new mixture onto ITO. Once you drop the aqueous solution of polypyrrole, it will dissolve the PEDOT:PSS.

I think you're looking at this the wrong way. Rather than trying to change the PEDOT:PSS (which will be tricky - PSS is anionic) you should consider changing your polymer. Alternatively, get rid of PEDOT:PSS and use another hole injection layer. (PEDOT:PSS is acidic and will etch the indium out of ITO.)

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  • $\begingroup$ Funny story.. The original aim of my PhD was to find something more conductive, more transparent and less acidic than PEDOT:PSS. $\endgroup$
    – Geoff Hutchison
    Feb 17, 2015 at 15:00
  • $\begingroup$ OK, I will start searching for a method of synthesizing polypyrrole in a different solvent. Thanks! $\endgroup$
    – dfghj
    Feb 18, 2015 at 1:43

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