R. Valaski

Influence of film thickness on charge transport of electrodeposited polypyrrole thin films

We report the investigation of charge transport properties of thin electrodeposited polypyrrole (PPy) films. The charge transport in these films is limited by thermionic injection and an expression for thermionic injection into low mobility materials is used to evaluate the energy barrier between electrodes (tin-oxide, Al and Ni) and PPy. Using the same expression, we estimate the positive charge carrier mobility, demonstrating that its value is higher for thinner films.

Charge injection and transport in electrochemical films of poly(3-hexylthiophene)

We have produced and characterized poly(3-hexylthiophene) (PHT) thin films by electrochemical deposition onto tin–oxide (TO) or gold covered glass substrates. PHT film thickness and roughness depend on deposition charge density and are also dependent on substrate material. From electrical measurements we determine an electrical conductivity of 9×10−5 S cm−1 when Ni and Au electrodes are used. An energy barrier of 0.8 eV for positive charge carrier injection into PHT at Al/PHT and TO/PHT interfaces was determined. We estimate the mobility of positive charge carriers in electrochemically deposited PHT as being 1×10−4 cm2 V−1 s−1. An energy diagram of PHT is proposed.We have produced and characterized poly(3-hexylthiophene) (PHT) thin films by electrochemical deposition onto tin–oxide (TO) or gold covered glass substrates. PHT film thickness and roughness depend on deposition charge density and are also dependent on substrate material. From electrical measurements we determine an electrical conductivity of 9×10−5 S cm−1 when Ni and Au electrodes are used. An energy barrier of 0.8 eV for positive charge carrier injection into PHT at Al/PHT and TO/PHT interfaces was determined. We estimate the mobility of positive charge carriers in electrochemically deposited PHT as being 1×10−4 cm2 V−1 s−1. An energy diagram of PHT is proposed.

The electronic behavior of poly(3-octylthiophene) electrochemically synthesized onto Au substrate

We investigate the electronic characteristics and the absorption spectra of poly(3-octylthiophene), POT, films grown by electrochemical methods onto Au substrates. We discuss the results considering the morphological factor. POT films thickness can be controlled by current density in the electropolymerization process. The film roughness depends on the thickness, being about 12% of film thickness. The samples for electrical measurements were made in sandwich structure, Au/POT/metal (metal: Ni, Al). Analyzing current-voltage data we were able to estimate the positive charge carrier mobility (5 x 10-4 cm2 V-1 s-1) and the potential barrier height in the metal/polymer interfaces (0.1 eV for Au/POT and Ni/POT and 0.85 eV for Al/POT).

The influence of electrode material on charge transport properties of polypyrrole thin films

We investigated electrodeposited polypyrrole (PPy) thin films. Tin-oxide (TO) and Au were used as deposition substrate and it was found that film morphology and roughness are strongly influenced by substrate choice. We determined the electrical conductivity of PPy films in Au/PPy/Ni, Au/PPy/Al, TO/PPy/Ni and TO/PPy/Al devices and estimated the positive charge carrier mobility and charge carrier concentration in PPy. Comparing the onset potentials for oxidation in the cyclic voltammograms of PPy and poly(3-methylthiophene) we constructed the energy levels diagram of PPy.