On the electronic transport properties of 4,4′-bipyridinium dibromides in thin films

The temperature dependences of electrical conductivity and Seebeck coefficient for 4,4′-bipyridinium dibromides thin films, deposited from dimethylformamide solutions, have been investigated. As-prepared compounds behave as n-type semiconductors, with activation energies of electrical conduction ranged between 1.60 and 1.83 eV. The ratio of charge carrier mobilities laid in the range 1.22–1.50. The study of optical absorption in the range 1.40–3.80 eV evidences direct optical gaps, as well as presence of an amorphous phase in examined compounds. Some correlations between semiconducting characteristics of investigated compounds and their chemical structure are established.