Mutsumi Suzuki

Electroluminescent features of oligothiophenes dispersed as a dopant in host matrices

The electroluminescent (EL) features of oligothiophenes dispersed as a dopant in the host matrices comprising tris(8-hydroxyquinoline)aluminum have been investigated. We chose the oligothiophenes that are substituted with phenyl or methyl groups at both the molecular terminals and possess various degrees of polymerization. Regarding both the phenyl- and methyl-substituted materials, the EL spectra are progressively red-shifted with the increasing number of thiophenes. Comparing these spectra with the photoluminescent spectra, we have found out that the EL arises mostly from the dopant molecules of the oligothiophenes. The emission is dominated by energy transfer from host matrices to the dopant molecules, leading to the enhanced device efficiencies. The specific effects of the phenyl- or methyl-substitution and the extension of the π-delocalization in the molecules are also discussed.