Impact of Eumelanin-PEDOT Blending: Increased PEDOT Crystalline Order and Packing-Conductivity Relationship in Ternary PEDOT:PSS:Eumelanin Thin Films

A recently developed protocol allows to prepare high quality thin films integrating eumelanin pigment with standard commercial poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The new blend combines noteworthy water stability and substrate adhesion with valuable electro-optical properties, so it can be used as anodic material in indium tin oxide-free organic light emitting diodes. Starting from these results, the present work systematically addresses the parameters affecting the blend conductivity. In particular, X-ray scattering analysis discloses that low quantities of eumelanin modifies molecular packing of the ternary blend, mainly in intermolecular distances and possibly in the degree of crystalline order of PEDOT, having anyway very little effect on the decay of the blend conductivity. Because of the synergetic effects observed here between the eumelanin and the PEDOT:PSS, this study provides a promising ground to access multifunctional materials for applications in advanced electronic devices and bioelectronics.