Regina M. Q. Mello

Hybrid metal-base transistor with base of sulfonated polyaniline and fullerene emitter

We demonstrate hybrid vertical architecture transistors that operate like metal-base transistors, using n-type silicon as the collector, sulfonated polyaniline as the base, and C60 fullerene as the emitter. Electrical measurements suggest that the sulfonated polyaniline base effectively screens the emitter from electric field variations occurring in the collector leading to the metal-base transistor behavior. These devices operate at low voltages and show common-emitter current gain equal to 8, which is independent of the base current up to values of ∼1.5μA and constant at collector voltages between 1 and 5V.

Vertical organic field effect transistor using sulfonated polyaniline/aluminum bilayer as intermediate electrode

We report a vertical organic field effect transistor using a bilayer formed by sulfonated polyaniline (SPAN) film and a thin Aluminum layer as the intermediate electrode. The device uses p-Si as gate, SiO2 as gate insulator, SPAN/Al bilayer as drain, C60 fullerene as channel and Ag as the source (top electrode). This device works at low voltages driving high current densities for organic field effect transistors, between source and drain, of the order of microamperes, with the additional advantage that the modulation occurs at both negative and positive gate voltages.

Efficient organic light-emitting diodes with fluorine-doped tin-oxide anode and electrochemically synthesized sulfonated polyaniline as hole transport layer

In this work we report efficiency measurements on light-emitting diodes with electrochemically synthesized sulfonated polyaniline as hole transport layer. The anode used in our devices is fluorine-doped tin oxide, the blocking layer is electrochemically synthesized poly(9,9-dioctyl-1,4-fluorenylenevinylene) and the electron transporting material and emitter is tris-(8-hydroxyquinoline) aluminum. Sulfonated polyaniline based devices presented efficiency of 0.79 cd/A.

Naphthalene Containing Poly(urethane-urea) for Volatile Memory Device Applications

Current of voltage controlled electrical switching in organic molecules and polymers is attracting attention due to its potential in organic electronic memory applications. The switching phenomenon under consideration in this article is characterized as a sudden transition from a low to a high conductivity condition at a threshold voltage. For the observed volatile switching phenomenom, the lower conductivity condition is restored as soon as the applied voltage becomes smaller than a holding voltage. This switching phenomenom presents the basic requirements for application in volatile memory devices. In this Communication we report on volatile electrical switching observed in a polyurethane derivative copolymerized with diaminonaphthalene.

Hybrid vertical transistor based on controlled lateral channel overflow

We propose and demonstrate a hybrid transistor based on a thin film of sulfonated polyaniline (SPAN) deposited on n-Si, forming a Schottky barrier. Two Al contacts deposited onto the SPAN act as source and control terminals. We find that the device operation involves two regimes of charge carrier transport as a function of the voltage applied to the drain: (i) a space-charge limited (SCL) regime at low voltages created by the electrons that diffuse from the Al electrodes and accumulate near the SPAN/Si interface and (ii) a thermionic regime at higher voltage where transport is limited by charge carrier injection over the Schottky barrier at the SPAN/Si interface. Due to the electric field enhancement near the edge of the source terminal, the voltage in the control terminal increases the Schottky effect near the SPAN/silicon interface in this regime. This mechanism permits the modulation of current reaching the drain by the voltage applied to control terminal. From the current-voltage characteristics of th...

A Solid Electrochromic Device Based on Poly(o­methoxyaniline) and Tungsten Oxide Electrochemically Synthetized

In this work a complementary organic-inorganic electrochromic device (DE) using solid polymeric electrolyte (EP) based on Poly(o-methoxyaniline) (POMA) and tungsten oxide (WO3) was assembled. The electrochromic materials were deposited by electrochemical method on ITO (indium tin oxide) coated glass and characterized in separate and under the device form. Characterization by cyclic voltammetry, spectrochronoamperometry, scan electronic microscopy, X-ray diffraction and perfilometry were carried out. The electrochromic behavior of the materials was studied in 650 nm, applying 1000 double potential steps. POMA films maintained 33% of the initial optical contrast. WO3 films presentedà a à i easeà ofà theà t a s itta eà a iatio à ΔTmax à ithà theà sta ilizatio à te de à i à 53%. The DE was produced according to the configuration ITO/POMA/(EP)/WO3/ITO, which presented sta leàΔTmax à àa ou dà %.àTheàelectrochromic films (POMA and WO3) and the DE presented in 650 ,à olo atio àeffi ie àη àa ou dà ,à 8àa dà à 2 C, respectively, and reduced response time