Ionic conduction and photoisomerization in azobenzene Langmuir-Blodgett films adsorbing cyanine dyes

Azobenzene (At) Langmuir-Blodgett (LB) films adsorbing cyanine dyes (NK-3) were deposited and the electrical properties were investigated in detail. The current vs electric field characteristics suggested ionic hopping conduction, and the transient current properties showed current peaks due to migration of mobile ions. The thermally stimulated currents (TSCs) were also due to the ionic space charge polarization, that is, displacement of mobile ions over long distances in the LB films. These results indicated that the electrical properties of the Az LB devices are strongly dependent on the mobile ions in the devices. In addition, the TSC and the short-circuit photocurrent properties due to the dyes were also changed by isomerization of the Az molecules. The results showed that the ionic space charge polarization and the aggregates of the dyes were affected by the isomerization.