Electrical properties of some new high resistivity organic semiconductors in thin films

Abstract

The temperature dependence of d.c. electrical conductivity, σ, and Seebeck's coefficient, S, for seven new synthesized 1-( p-R-benzoyl)-1,2,3,3 a-tetrahydropyrrolo-[1,2- a][1,10]-phenanthrolin-2,3-( N-R′)-dicarboximide compounds, has been investigated. Thin film samples ( d = 0.09–0.94 μm) deposited from dimethylformamide solutions, by an immersion technique, onto glass were used. X-ray diffraction (XRD) analyses were performed for the investigation of crystalline structure of as-prepared films, while atomic force microscopy (AFM) technique, corroborated to optical microscopy was used for the examination of surface morphology. The behavior of σ and S as a function of temperature is typical for polycrystalline semiconducting (n-type) materials. The activation energy of electrical conduction laid in the range 1.21–1.82 eV, while the ratio of charge carrier mobilities ranged between 1.05 and 1.15. Some correlations between semiconducting properties and molecular structure of the compounds were established. The model based on band gap representation can be satisfactory used for the explanation of electronic transport in investigated compounds.