Electroluminescence (EL) characteristics of the double-MPc-layered devices consisting of ITO/MPc1/MPc2/Alq3/Mg-Ag were investigated, where MPc1 and MPc2 represent two metallophthalocyanines and Alq3 stands for tris(8-quinolinolato)aluminum(III). A compatible double-MPc-layered structure led to a decreased hole-injection barrier at the ITO/MPc1 interface and an increased electronblocking ability of the MPc2 layer in the device. The EL efficiency of the device was improved further by using a 4,40-bis(m-tolyphenylamino) biphenyl (TPD) layer as an additional hole-transport layer due to its good electron-blocking ability. For the double-MPc-layered devices with a TPD layer, the EL performances were dependent primarily on the electronic structure of ITO/MPc1 interface rather than that of MPc1/ MPc2 or MPc2/TPD interface.

Electrochemical oxidation of thin films of s-p-conjugated thienylene-silanylene copolymers, with poly[(hexamethyltrisilanylene) quinque(2,5-thienylene)] (TS5T) as a representative, is investigated in acetonitrile solutions containing different electrolytes. It is found from fluorescence spectroelectrochemical, electrochemical quartz crystal microbalance and FT-IR measurements that Si-Si-Si s-bonding is weakened by electrochemical anion doping in p-conjugated segments of the polymer, resulting in promotion of cleavage of the s-bonding in BF4 and PF6 solutions. Such a doping-enhanced cleavage of the Si-Si-Si bonding is relatively negligible in a ClO4 solution, suggesting some specific interaction between the Si atoms in the polymer chain and the F atoms in BF4 and PF6 anions. In a F solution, on the other hand, the polymer film undergoes electrochemical fluorination and:or chemical dissolution.

Electrochemical stability of polywtetraethyldisilanylene.oligo2,5-thienylene.x DSmT; m refers to the number of thienylene units. films is investigated by means of in situ UV-vis-NIR spectroscopy, in situ and ex situ fluorescence spectroscopy, gel-permeation chromatography, and FT-IR spectroscopy. It is found that a Si-Si bond in DSmT film with ms3 to 5 is cleaved at potentials as low as 0.5 V versus AgrAgq in acetonitrile, resulting in dissolution of oligothiophene-like species. The decomposed products are oxidized to form another polymer film on the surface of an original DSmT film and a doping reaction observed earlier takes place on the composite polymer film. q1998 Elsevier Science S.A. All rights reserved.

Electropolymerization of aniline-2,5-disulfonic acid in aqueous solutions results in formation of a water-soluble self-doped polymer. E€ects of synthesis conditions were investigated on conductivity and molecular-weight distribution of the polymer. The polymer shows solubility in water high up to 109 mg cm-3. The conductivity of the polymer, with best value of about 0.34 S cm-1, is independent on pH up to at least pH 9.

Electrochemistry of s-p-conjugated polymers, poly[(hexamethyltrisilanylene)oligo(2,5-thienylene)] has been investigated in acetonitrile by using cyclic voltammetric and spectroelectrochemical techniques. Cyclic voltammograms of these polymers films display generally two pairs of main redox peaks, indicating the doping and dedoping processes of the polymers. The electrochemical oxidation of the polymer films results in their partial decomposition, besides the doping, which is shown by electrochemical quartz crystal microbalance and spectroelectrochemical measurements. The decomposition products are characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, FT-IR, and GPC measurements. It is concluded that the decomposition originates mainly from electrochemical cleavage of silicon-silicon bonds in the polymer chains, and the electrochemical stability of the s-p-conjugated polymers may be improved by decreasing the oligosilanylene block size in the polymer chains.