Cycle life, stability, and characteristics of color switching cells utilizing polythiophene films

Cycle life, stability, and switching characteristics of a color switching device utilizing a conducting polymer, polythiophene film in an electrochemical cell are studied. Cycle life of more than 5×105 times has been achieved by operation with an appropriate rectangular voltage application in an electrolyte of Pb(ClO4)2/acetonitrile. A chronoabsorptometric measurement is carried out to inspect the kinetics of electrochemical cycle. The diffusion of charged species in the film is found to control the switching time and its constant is evaluated to be 10−12–10−10 cm2/s as a function of applied voltage. The doping mechanism and dopant distribution profiles in the film are proposed for various conditions of applied voltages. Stability and cycle life of the cell during switching, and memory state under an applied voltage are discussed in terms of the degradation of polythiophene film.