PENDIDIKAN

Ž . Ž . The photoluminescence PL and electroluminescence EL of poly 3-decylmethoxythiophene have been studied for devices Ž . fabricated using both the spin-coating, and Langmuir-Blodgett LB technique. Strong thermochromic effects in the PL, correlated to a thermal transition in the polymer, are observed for the spin-coated films while negligible thermal dependence of the PL is observed in the LB films. A blue shift of the EL with respect to PL is observed for the LB films and is associated to partial polymer degradation. By analysing the time evolution of EL during the first minutes of device operation, the processes related to annealing and Al diffusion at the electroderpolymer interface are discussed. q 1998 Elsevier Science S.A. All rights reserved.

Akylthio-group-substituted phthalocyanine rare-earth metal sandwich complexes such as bis[octakis(alkylthio)phthalocyanineato]europium(III) {[(CnS) 8Pc]2Eu}, bis[octakis(alkylthio)phthalocyaninato]lutetium(III) {[(CnS) 8Pc]2Lu}, bis[octakis(alkylthio)phthalocyaninato]terbium(lII) {[(CnS) 8Pc]2Tb} exhibit discotic liquid crystal phases. Photoluminescence (PL) peaks of [(CnS)8Pc]2 Eu were observed at around 400-600 nm and 730 nm in chloroform solution. However, the strong narrow emission of the Eu3+ ion was not observed compared with other Eu-complexes. The intensity and the decay time of the PL peak depend strongly on the phase. They have been explained by taking electronic energy schemes of both phthalocyanine ligands and the Eu3+ ion into consideration. The role of the triplet exciton is also discussed. In the photoconductivity (PC) spectra of [(CnS)8Pc]2Eu several peaks were observed corresponding to the absorption peaks. The behavior has been discussed in terms of carrier migration along the stack of phthalocyanine cores in the discotic phase. Current-voltage characteristics and dielectric properties of these discotic liquid crystals have also been clarified

Intense photoluminescence ( PL 1 is observed in di-subatituted polyacetylene derivatives even though solitonic mid-gap absorption is observed upon doping. contrary to non-subhtitutrd rrcirls-polyacetylene and mono-substituted polyacetylene in which strong PL is not observed. Intense green and blue electroluminescence (EL) is realized utilizing poly( diphenylacetylene) derivatives and poly( I-alkyl-2-phenylacetylene) derivatives, respectively. Greenish-blue emission is also observed in poly( 1 -chloro-2-phenylacetylene) derivatives. The dependence of wavelength and intensity ot' PL and EL on the molecular structure of substituents is clarified in detail. The effects of molecular alignment and layer structure on the EL characteristics are also discussed. Upon intense light excitation, remarkable spectral narrowing due to stimulated emission is also observed in these di-substituted polyacetylene derivatives. 0 1997 Elsevier Science S.A.

The electrical characteristics and photoirradiation effects of a conducting polymer/C60 heterojunction device with C,, doped conducting polymer layer were investigated in contrast to those of non-doped device. The C,, doping to conducting polymer layer should be effective not only to improve short circuit photocurrent but also to reduce the serial resistance of the conducting polymer layer. Both effects can be interpreted in terms of photoinduced charge transfer between conducting polymer and C,,.

Study on the incorporation of trivalent europium (Eu 3+ ) complex into polymerizable macrocylic molecules, namely calixarene and calixresorcinarene derivatives, has been carried out. Broadening of hypersensitive luminescence peak was observed in solution and polymer containing a compound of europium complex and calixresorcinarene monomer, which is ascribed to ligand field splitting due to anisotropic local field at the Eu 3+ ion site. From 1 H NMR spectroscopy, it is found that the chemical shift originated from the moiety at the upper rim of calixresorcinarene is remarkably downfield shifted. Pseudocontact shift analysis suggests that binding between Eu 3+ ion and calixresorcinarene monomer is formed at the Eu 3+ second coordination sphere. These experimental results show that the binding does not alter nephelauxetic effect of the Eu 3+ first coordination shell, but only slightly change coordination structure and symmetry. Nevertheless, the binding results in longer luminescence lifetime in comparison to the case of pure europium complex indicating significant reduction of non-radiative decay.