Newly synthesized fused heterocyclic compounds in thin films with semiconductor properties

Abstract

Temperature-dependent electrical conductivity and thermoelectric power of some recently synthesized fused heterocyclic compounds (nonsymmetrical bisindolizines), are studied. Thin-film samples ( d = 0.10–0.20 μm) deposited from dichloromethane solutions onto glass substrates were used. Organic films with reproducible electronic transport properties can be obtained if, after deposition, they are submitted to a heat treatment within temperature range 300–600 K. The studied compounds show typical p-type semiconductor behavior. The activation energy of the electrical conduction ranges between 0.90 and 1.17 eV, while the ratio of charge carrier mobilities was found in the range 0.94–0.97. Some correlations between semiconducting parameters and molecular structure of the organic compounds have been discussed. In the higher temperature range (373–601 K), the electronic transport in examined compounds can be interpreted in terms of the band gap representation model, while in the lower temperature range, the Mott's variable-range hopping conduction model was found to be appropriate.