PROPERTIES AND MICROSTRUCTURE OF CRYSTALLINE BEDT-TTF POLYIODIDE NETWORK IN POLYCARBONATE MATRIX

A conducting network of crystalline [bis(ethylenodithio)tetrathiafulva lene]I-2(3) (ET(2)I(3)) can be formed within the surface layer of poly carbonate by exposure of films containing 2 wt.% of molecularly disper sed ET to vapours of iodine solution in CH2CI2, THF or TCE. The relati onship between the microstructure and properties of conducting network s formed under different conditions is reported, Depending on the iodi ne concentration in the solution, the kind of solvent and the treatmen t time, networks of alpha-ET(2)I(3) or beta-ET(2)I(3) crystallites are formed. Their preferential orientation (c-axis perpendicular to the f ilm plane) can be deduced from X-ray diffraction. Morphological studie s performed using a scanning electron microscope revealed a nanoscopic size of crystallites and different habits: plate-like or river-stone- like. The presence of a less organised layer covering the crystallites , possibly formed of salts of another composition, is also discussed. The conductivity of the films is higher than that reported for polycry stalline layers obtained by the evaporation method and for pressed pel lets of ET(2)I(3). Films with alpha-ET(2)I(3) show semiconducting beha viour with some deviation of the temperature dependence of conductivit y at 160-200 K. Films with beta-ET(2)I(3) show metallic conductivity d own to 60 K. Studies of the optical absorption have shown that the con ducting network does not contribute much to the UV-VIS spectra of cond ucting films.