Application of impedance spectroscopy to the study of organic multilayer devices

The application of electrical impedance spectroscopy to gas sensors and light emitting devices (LEDs) based on Langmuir–Blodgett (LB) films is reviewed. The sensing material was a co-ordination polymer formed by reaction of the bifunctional amphiphilic ligand 5,5′-methylenebis (N-hexadecylsalicylideneamine)) (MBSH) and copper ions in an interfacial reaction at the water surface. Changes of the device capacitance and conductance during exposure to ethanol, acetonitrile and benzene were related to the polarity of the organic vapour. Impedance measurements on LEDs incorporating a substituted polypyridine derivative, poly(6-hexyl-2,5-pyridinediyl), provided an understanding of the equivalent circuit of the device structure.