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Improving the electrical conductivity and structural properties of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) for thin film and flexible electronics

Charas, A. ; Silva, S. ; Ablú, A. ; Príncipe, C. ; Santos, L. ; Galvão, A. ; Morgado, J.

Improving the electrical conductivity and structural properties of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) for thin film and flexible electronics, Proc Sociedade Portuguesa de Química EuChemS Chemistry Congress (ECC8) ECC8, Lisbon, Portugal, Vol. , pp. - , August, 2022.

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Abstract
Poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is one of the most important intrinsically conducting polymers, owing to its water dispersibility which allows its use as an easily processed aqueous conducting «ink», high thermal stability, electrochemical activity, high transparency in the visible range, and excellent biocompatibility. Nevertheless, although PEDOT:PSS´ applicability is superior among conducting polymers, its electrical conductivity is low and long-term stability against aqueous media must be improved for some applications, such as thin film transparent electrodes or electrically active components for the bioelectronics field.
In this communication, we show that oxetane reagents containing alcohol groups, as additives in PEDOT:PSS aqueous dispersions, can remarkably improve the conductivity (in more than 3 orders of magnitude) and structural stability of PEDOT:PSS thin films against aqueous medium, while maintaining their transparency in the visible [1]. As a result, the developed polymer layers are suitable for applications as the transparent electrode in thin film optoelectronic devices, such as organic photovoltaic devices. It was found that the oxetane reagents produce graft copolymers, composed of polyether blocks anchoring PSS chains, and such structural changes are at the origin of the enhanced conductivity and improved films ‘stability. In addition, the modified PEDOT:PSS dispersions, besides enabling preparing thin films by the spin-coating method, are also suitable for high-resolution ink-jet printing, allowing to produce micron-wide conducting wires. Moreover, free-standing and mechanically flexible films could be obtained from the new PEDOT:PSS formulations, this opening the pathway for applications on flexible electronic devices, as medical sensors and others