Electrical and optical properties of some polyazomethine thin films prepared by a spin-coating method

Three types of polymers containing azomethine units linked by ether bond, sulfone and bisfenols, were prepared, dissolved in dimethylformamide and deposited on glass slides by spin coating. The obtained transparent thin films exhibit an amorphous structure with morphology dependent on chemical structure. The study of optical absorption evidenced large direct band gaps. The sulfone presence induces an increase in the thin film band gap energy and a decrease in Urbach energy and low-energy absorption coefficient. The temperature dependence of the electrical conductivity showed that thin films have semiconducting properties with two distinct sections. The mechanism of electronic transport is described. The values of the energy band gap determined from absorption spectra were in good agreement with those calculated from the temperature dependence of the electrical conductivity. In the low temperature range, the temperature dependence of the electrical conductivity was described by the Mott variable range hopping model. (Recieved July 4, 2011; accepted July 25, 2011)