Fabrication, characterization and electroluminescent properties of ultrathin multilayered films with conjugated polymers via spin self-assembly method

Abstract

This study is on the π-conjugated polymers with semiconducting properties which are recently attracted much attention due to their applicability in the field of optic and optoelectronic devices such as light-emitting diodes (LEDs) and laser. Our research on these conjugated polymers and related optoelectronic devices are focused on the points to enhance their environmental stability and to control them in the molecular scale. To achieve these goals, two approaches were accomplished. First, conjugated polymer/layered silicate hybrid nanocomposite system was studied. Second, conjugated polymer/layered silicate well-ordered multilayer ultrathin film via spin self-assembly method was studied. Polymer-rich/clay-rich phase-separated polymer-layered silicate nanocomposites are prepared through a solution blending of poly(xylylidene tetrahydrothiophenium chloride) with two kinds of layered silicates. By spin-coating, thin films of each phase were obtained, followed by thermal elimination of tetrahydrothiophene and HCl to final poly(p-phenylenevinylene) (PPV)/layered silicate nanocomposite. At ambient conditions, the PPV films are easily photodegraded due to the oxygen diffused in. Poly(p-phenylene vinylene)/layered silicate nanocomposite showed improved environmental stability against photodegradation under an air ambient condition. And optical absorption and photoluminescence measurements demonstrate that the thin films of clay-rich phase are much less photodegraded than those of polymer-rich and PPV reference. Well-ordered multilayer ultrathin films with anionic layered silicate sheets and precursor of poly(p-phenylene vinylene) as polycation could be fabricated through layer-by-layer spin self-assembly method and characterized by contact angle measurement, UV/Vis spectroscopy, X-ray reflectivity and atomic force microscopy. Due to the simple procedure of spin self-assembly consisting of repetitive dropping, spin-coating and spin-washing of oppositely charged materia...