STABILITY OF N-TYPE DOPED CONDUCTING POLYMERS AND CONSEQUENCES FOR POLYMERIC MICROELECTRONIC DEVICES

Present polymeric microelectronic devices are typically unipolar devic es, based on p-type semiconducting polymers. Bipolar devices stable un der ambient conditions are desirable, but have not yet been reported d ue to a lack of stable n-type doped conducting polymers. Starting from the standard redox potentials of, especially, water and oxygen, stabi lity requirements on electrode potentials of n-type doped conducting p olymers are derived. The predictions are then compared with experiment al data on stability of conducting polymers. A good agreement is obtai ned. An electrode potential of about 0 to +0.5 V (SCE) is required for stable n-type doped polymers, similar to the requirement on the elect rode potential for stable undoped p-type polymers. Consequences for bi polar devices are analysed. Huge overpotentials for the redox reaction with wet oxygen are required in order to realize thermodynamically st able bipolar devices from known doped p-type and n-type conducting pol ymers. Finally, possible solutions, accepting thermodynamic instabilit y, are discussed.