Electron transport properties of some newly synthesized nonsymmetrical bisindolizines in thin films

In this work, temperature dependences of electrical conductivity and thermoelectric power, for some recently synthesized nonsymmetrical bisindolizines, are studied. Thin-film samples (d = 0.10–0.30 μm) spin-coated from dichloromethane solutions onto glass substrates were used. Organic films with reproducible electronic transport properties can be obtained if, after deposition, they are subjected to a heat treatment within the temperature range of 301–541 K.The studied organic compounds show typical p-type semiconductor behavior. The activation energy of electrical conduction was found in the range 1.00–1.26 eV, while the ratio of charge carrier mobilities ranged between 0.90 and 0.97.The correlations between determined semiconducting parameters and specific features of molecular structure of the compounds have been discussed.In the higher temperature range (363–541 K), the electronic transport in actual compounds can be interpreted by using the band gap representation model, while for lower temperatures, Mott's variable-range hopping conduction model was found to be appropriate.