Interplay of monomers, dimers and J-aggregates of thiamonomethinecyanine dye with PEDOT and PSS in the dye–PEDOT:PSS composite system

• New composite system of thiamonomethinecyanine dye and PEDOT:PSS.
• Suppressed formation of J-aggregates in the presence of PSS.
• Nontrivial behavior of conductivity depending on dye aggregation in the composite film.
• Conformational changes of PEDOT through interaction with sulfonic groups of the dye.

Mutual influence of thiamonomethinecyanine dye and PEDOT:PSS in the dye–polymer composite solutions and films was studied. It was found that PSS tends to suppress formation of J-aggregates of the dye molecules in the solution, while there is a competition between sulfonic groups of dye and PSS for binding with the PEDOT backbone. Interaction of dye monomers with PEDOT:PSS at relatively small dye concentration in the composite film was found to suppress film conductivity, while dimerization of the dye molecules at higher concentration resumes conductivity of the composite film. Suppressed conductivity upon interaction of the dye and PEDOT backbone was explained by steric disparity of the distance between sulfonic groups of the dye molecule and the distance between positive sites of the planar PEDOT backbone which induces deformation of the latter.

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