Showing papers by "Franco Cacialli published in 1994"
TL;DR: In this paper, a light-emitting diodes fabricated with a layer of poly( p -phenylenevinylene) (PPV) sandwiched between electrodes of indium-tin oxide (ITO) and calcium have been studied over extended periods of operation.
63 citations
TL;DR: In this paper, the effects of various vapours on the power spectrum of the resistance fluctuation of polypyrrole thin-film resistors were studied and an ultra-low noise amplifier and current source were built in order to detect the very low signal and bias the resistors.
Abstract: The effects of various vapours on the power spectrum of the resistance fluctuation of polypyrrole thin-film resistors were studied. An ultra-low noise amplifier and current source were built in order to detect the very low signal and bias the resistors. The samples were obtained by means of chemical vapour deposition on to oxidizing precursors. The method was successfully extended to n-methylpyrrole and thiophene polymerization.
45 citations
TL;DR: In this paper, a new poly(phenylene- co -dialkoxyphenylene) derivative was synthesized by the Suzuki coupling of aromatic bromoboronic acids, which showed strong violet photoluminescence (peak 415 nm) in the solid state and good solubility in organic solvents.
39 citations
TL;DR: In this article, low-frequency resistance fluctuations were measured on polypyrrole thin-film resistors and the dependence of the noise magnitude on the applied dc voltage was studied revealing that the noise cannot be ascribed only to equilibrium resistance fluctuations.
Abstract: Low‐frequency resistance fluctuations were measured on polypyrrole thin‐film resistors. The samples were obtained by chemical‐vapor deposition onto copper chloride patterned precursors. The measurements were devoted to characterize the noise spectral density of constant‐current‐biased samples. The dependence of the noise magnitude on the applied dc voltage was studied revealing that the noise cannot be ascribed only to equilibrium resistance fluctuations. Application of the Hooge formula provided an estimate of carrier density in the material.
19 citations
01 Jan 1994
TL;DR: In this paper, a conjugated polymer with high electron affinity, a cyano derivative of poly (p-phenylene vinylene), was proposed for use as the electron transporting layer in heterostructure LEDs.
Abstract: Conjugated polymers can be use to provide charge transport and emissive layers in a range of thin-film electroluminescent devices. Electroluminescence results from radiative decay of excitons which are formed by electron-hole capture. Device efficiency is particularly sensitive to the balancing of electron and hole currents injected from opposite electrodes, and this is best achieved at the heterojunction between two polymer layers with different electronegativities. We report here the properties of a conjugated polymer with high electron affinity, a cyano derivative of poly (p-phenylene vinylene), PPV. This polymer shows an electron affinity considerably higher than than that of PPV, and is therefore suitable for use as the electron transporting layer in heterostructure LEDs. It shows efficient photoluminescence due to radiative decay of singlet excitons, and photoinduced absorption in the IR, similar to that in PPV, which we attribute to excitations of photogenerated triplet excitons. EL devices formed with a heterojunction between PPV and this cyano derivative of PPV, with indium/tin oxide as positive electrode, PPV, cyano-PPV layers and an aluminium negative electrode, show internal quantum efficiencies as high as 4%.
6 citations