Structure and optical properties of polycarbonate films with microcrystallites of BEDT-TTF polyiodides

The morphology, structure and optical properties of thin layers of crystalline bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) polyiodides formed within the surface layer of polycarbonate film were investigated. The samples were obtained by exposing the polymer films containing 2 wt.% of molecularly dispersed ET to vapors of I2/CH2Cl2 solutions of different I2 concentration. X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM) show that, depending on the preparation conditions, ET polyiodides form plate-like crystals, flakes and some less organized layer covering microcrystallites. In all cases only (001) reflexes attributed to the α-ET2I3 phase were registered in the X-ray diffraction (XRD) experiments. Reaction of iodine with already formed crystals leads to new morphological structures. Using saturated iodine solutions the nonconducting polyiodides are formed which, under ambient conditions, undergo transformation into a stable conducting salt.