Exciton Dynamics in re-conjugated Polymers and Its Application to High Performance Solid Laser

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Various types of n-conjugated polymers have been designed and synthesized to realized a novel solid laser with a high performance and their electronic and optical characteristics have been investigated. The electronic and optical properties such as a photo-excited electronic state in polyacetylene derivatives having various substituents have been investigated by a UV-visible absorption and luminescence measurements and a life time measurement of the luminescence. The relationship between electronic state and molecular structure in π-conjugated polymers with hetero main chain structures including Si atom has been investigated, and it is found that the effective π-conjugation length can be controlled by the introduction of Si atom. Fabrication techniques for solid lasers such as a spin coating and self-assembly methods have been improved and light emission characteristics have been investigated. Based on a nonlinear photoconductivity upon a high intensity excitation in the π-conjugated polymers, an excitation process for the photoconduction has been revealed by means of a pump and probe technique using a femto second high intensity laser. It is found that a polaron pair plays an important role in a photo-excitation process in π-conjugated polymers. The inverse opal of π-conjugated polymer has been fabricated. Poly(3-alkylthiophene) is infiltrated into nano-scale voids of SiO_2 synthetic opal in the melted state and subsequently SiO_2 spheres is removed by a chemical treatment, resulting in the conjugated polymer inverse opal. The reflection spectrum of the polymer inverse opal can be controlled by a thermal treatment and electrochemical doping, which is interpreted to be due to a refractive index change in poly(3-alkylthiophene) based on the change in electronic state upon the temperature change and electrochemical doping.