Organic π−conjugated compounds have experienced over the last decades a tremendous interest as versatile and highly performing active components in a large variety of devices and applications. Two peculiar characteristics of organic materials are key for their technological exploitation. Firstly, most organic conjugated materials can be manufactured by low cost, solution based deposition techniques. Moreover, the intrinsic flexibility of both their electrochemical and optical properties holds promises for custom designed active materials. On this respect, the formulation of general structure-property relationships is a key requirement.

This talk will address the main characteristics connected with reversible redox behaviour in conjugated materials: charge transport capabilities and tuning of optical properties. The discussion will focus on the structural design required for the preparation of preferentially n or p dopable semiconducting polythiophenes derivates highlighting the role of heteroaromatic compounds as intrinsically electron excessive or electron deficient building blocks. The role of solid state interactions in both single and multi component thin layers will then describe, focusing on recent examples of organic-based electrochromic devices developed in the frame of the EELICON FP7 project.