Electrical d.c. conduction mechanism in some newly synthesized mono- and dipyridine quaternary salts in thin films

Abstract The study of temperature dependence of the electrical conductivity and thermoelectric power, for some recently synthesized quaternary salts of bipyridine and indolisine pyridine, is reported. Thin film samples ( d  = 0.10–0.60 μm) deposited from dimethylformamide 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 290–500 K. The studied organic salts behave as typical p-type semiconductors. The activation energy of electrical conduction laid in the range 1.40–1.75 eV, while the ratio of charge carrier mobilities ranged between 0.77 and 0.93. The correlations between determined semiconducting parameters and specific molecular structure of the compounds have been discussed. In the higher temperature range (360–500 K), the electronic transport in examined compounds can be interpreted in terms of band gap representation model, while for lower temperatures, Mott's variable-range hopping conduction model may be conveniently used.