Electroactive materials are playing an ever increasing role in science and technology. At present the wide range of applications for these materials include electrodes and membranes for electrochemical energy conversion and storage, electroceramic devices and sensors, organic diodes, magnetic and optical devices, and photoresists. The book summarizes the results of the special research program 'Electroactive Materials' established by the Austrian Science Fund. Contributions deal with plastic solar cells (invited review); conjugated polymers and organosilanes; thin-film zinc/manganese dioxide electrodes; the anode/electrolyte interface in lithium ion batteries; a novel technique for manufacturing highly conductive composite materials; a new method for conductivity relaxation measurements on mixed conductors; the application of surface science to thin films and interfaces of electroactive organic materials; preparation and radical oligomerisation of an Fe(II) complex without loss of spin-crossover properties; phase gratings in photoreactive polymers as a way to optically pumped organic lasers; and high-spatial resolution elemental analysis and mapping by analytical electron microscopy.