Stability of n-type doped conducting polymers and consequences for polymeric microelectronic devices

Present polymeric microelectronic devices are typically unipolar devices, based on p-type semiconducting polymers. Bipolar devices stable under ambient conditions are desirable, but have not yet been reported due to a lack of stable n-type doped conducting polymers. Starting from the standard redox potentials of, especially, water and oxygen, stability requirements on electrode potentials of n-type doped conducting polymers are derived. The predictions are then compared with experimental data on stability of conducting polymers. A good agreement is obtained. 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 electrode potential for stable undoped p-type polymers. Consequences for bipolar devices are analysed. Huge overpotentials for the redox reaction with wet oxygen are required in order to realize thermodynamically stable bipolar devices from known doped p-type and n-type conducting polymers. Finally, possible solutions, accepting thermodynamic instability, are discussed.