Saturated red light emission from organic light emitting diodes is less common than emission in the green or the blue. Most organic red light emitting devices are based on rare earth complexes, mainly europium, which are known to exhibit stability problems. The present article describes new diodes made of indium tin oxide-coated glass/triphenylene hexaether/perylene tetraester/aluminum. The band diagram was determined by ultraviolet photoemission spectroscopy, cyclic voltammetry, scanning tunneling microscopy, and absorbance measurements. The interfaces between electrodes and organic layers were investigated by x-ray photoelectron spectroscopy. The current–voltage and luminance–voltage characteristics are very reproducible from device to device, with an emission peak at 620 nm and a full width at half maximum of 80 nm, a current rectification ratio of about 30, I∼V2 at low voltages and I∼Lum∼V6 at higher voltages.

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X-ray photoelectron spectroscopy has been used to study the chemical structure of stoichiometric SiO thin films. The Si 2p line of silicon binding energy is found at 101.7 eV, and deconvoluted spectra show that at least four distributions of the type Si-(Si4-yOy) exist in the films. The result is consistent with a random-binding model but differ from it for quantitative distribution. The interfacial layer between the SiO thin film and a nickel electrode has also been investigated by the same technique. Chemical reactions are found to occur between the oxide and nickel ions to form silicides: Ni2Si at the interface and NiSi deep inside the insulator. A probable diffusion of both Si and Ni atoms divides the insulator into two regions: one which is rich in Si at the interface and the other rich in SiO2 in the insulator. The results obtained explain qualitatively some electrical properties of the metal-SiO-metal structures.

Thin films of poly(methyl methacrylate)–multiwalled nanotubes composites were produced by spin coating using different nanotube concentrations. The materials were characterized by scanning electron microscopy, energy-dispersive x-ray analysis, and Raman spectroscopy to obtain information on the possible interactions between the constituents and to control the homogeneity of the films. Electrical conductivity measurements of the composites, as a function of the nanotube concentration, show a percolation threshold at very low concentration. Also, the J–E characteristics exhibits a nonlinear behavior at low concentration, becoming linear far above the threshold.

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Communications[I21 The current ratios, ipJiQc, were near unity. They and the half-wave oxidation potentials were independent of the scan rate I>. The anodic peak current. ; , , a. was proportional to v1 *.[I31 R. L. Myers. 1. Shain. A n d . C h n . 1969. 4 f , 980.[14] The neutral and dicatioii states may be formed in the crystals by disproportionation as in solution. The intensity of the ESR signal of the 2d -PF, salt is weaker than that of the usual cation radical salts, suggesting the contribution of those states. A detailed study is underway. 1151 PM3 calculations (MOPAC program; J. J. P. Stewart, J. Cornput. Chem. 1989, 10. 209, 221) were performed by using the geometry determined by the X-ray analysis.

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