Electron transport properties of some new 4-tert-butylcalix[4]arene derivatives in thin films

Abstract

Temperature dependences of electric conductivity and thermoelectric power of some recently synthesized organic compounds, 4-tert-butylcalix[4]arene derivatives, are studied. Thin-film samples (d = 0.10–0.40 μm) spin-coated from chloroform solutions onto glass substrates were used. Organic films with reproducible electron transport properties can be obtained if, after deposition, they are submitted to a heat treatment within temperature range of 295–575 K.The studied polycrystalline compounds show typical p-type semiconductor behavior. The activation energy of the electric conduction ranges between 0.82 and 1.12 eV, while the ratio of charge carrier mobilities was found in the range of 0.83–0.94.Some correlations between semiconducting parameters and molecular structure of the organic compounds have been discussed.In the higher temperature ranges (T > 420 K), the electron 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.The investigated compounds hold promise for thermistor applications.