You have to design an experimental procedure and optimize the post treatment conditions to get desired results.

The structure / conductivity relationship in conductive polymers has not been revealed yet for most conductive polymers. I would assume that in PEDOT-PSS very broadly spoken we are dealing with a similar situation as in Polyaniline (PAni). For an overview, please read:

Chapter Conductive Polymers as Organic Nanometals

For answering your question, 3 aspects need to be considered:

1) Conductive polymers have a morphology consisting of primary particles with about 10 nm size; electrons need to tunnel between the particles (from particle to particle, tunneling barriers need to be overcome,

see Article Fully protonated polyaniline: Hopping transport on a mesoscopic scale

- this tells you: whatever you can do to weaken the tunneling barriers will increase conductivity, various polar solvents may act in this direction

2) PSS is by far less homogeneously distributed within PEDOT than (e.g.) pTs is within PAni particles.

- this tells you: whatever you can do to improve homogeneity, may increase conductivity, and polar solvent molecules may be able to help

3) Within the particles, the conductive polymer chain arrangement - to my knowledge - has not been elucidated for PEDOT yet, for PAni I concluded it is helical, see here:

Article New Insight into Organic Metal Polyaniline Morphology and Structure

I would assume that PEDOT also is helically structured, and also PEDOT has relatiovely short chain length;

- this tells you: whatever you can do to achieve an arrangement of the short helices which create an effectively longer helix along whose axis electrons can travel, will increase conductivity, and polar solvent molecules may help here to improve the arrangement (in PAni, I did it with the shear forces during dispersion)

# Bernhard Wessling thank you very much for your more elaborated answers.As you said, there will be structural rearrangement of Both PEDOT and PSS from coil to almost straight structure. and hence conductivity will also increases, since the sheet resistance will decrease due to the structural modification. But I did not get any clue how and why the work function of PEDOT:PSS get decreased. Of course work function (WF) will decrease when the binding energy gets decreased. For example, PEDOT:PSS PVP AI4083, changes its WF from 5.064 eV to 4.88 eV after treated with Methanol when I measured using kelvin Probe. Is it due to the removal of some PSS (which is longer chain and insulator) during the post treatment by polar solvents? How could I relate the solvent treatment to the binding energy of the PEDOT:PSS so that to know the real cause for the change in WF?

Thank you all once again for you answers!

Zekarias, I did not say that structural rearrangement of PEDOT and PSS would go from coil to almost straight structures, because

1.) I did not study PEDOT-PSS structure

2.) for PAni, which I studied and showed you, such rearrangement does not happen that way, but the helical (not "coil"!) subunit arrange each other so that they apparently form a longer helix

3.) both PAni and PEDOT chanins are extremely stiff.

Work function is dependant upon many variables, one of which is the composition of the outer surface! by rinsing, you change work function!

Also, when performing a structural rearrangement, the properties of this conductor changes hence work function changes.