Electrochemical Switching in Conducting Polymers – Printing Paper Electronics

Sammanfattning: During the last 30 years a new research and technology field of organic electronic materials has grown thanks to a groundbreaking discovery made during the late 70’s. This new field is today a worldwide research effort focusing on exploring a new class of materials that also enable many new areas of electronics applications. The reason behind the success of organic electronics is the flexibility to develop materials with new functionalities via clever chemical design and the possibility to use low?cost production techniques to manufacture devices.This thesis reports different aspects of electrochemical applications of organic electronics. We have shown that the color contrast in reflective and transmissive electrochromic displays can be almost doubled by adding an extra electrochromic polymer. The choice of electrochromic material was found to be limited by its electrochemical over?oxidation (ECO) properties, which is one of the main degradation mechanisms found in displays. The irreversible and non?conducting nature of over?oxidized films encouraged us to use it in a novel patterning process in which polythiophene films can be patterned through local and controlled deactivation of the conductivity. ECO can be combined with various patterning tools such as screen printing for low?cost roll?to?roll manufacturing or photolithography, which enables patterning of small features. Studies have shown that electronic conductivity contrasts beyond 107 can be achieved, which is enough for various simple electronic systems. To generate better understanding of the ECO phenomenon, the effect of pH on the over?oxidation characteristics was studied. The results suggest that a part of the mechanism for over?oxidation depends on the OH– concentration of the electrolyte used. Over?oxidation has also been used in electrochemical loggers, where the temperature and time dependence of the propagation of an over?oxidation front is used to monitor and record the temperature of a package.