Plasmonic Organic Electronic Devices

Abstract

Surface plasmon is a collective oscillation behavior of electrons in metal nanoparticle induced by the excitation of incident light, which can create an enhanced localized electric field near the surface of metal nanoparticle. To date, metal nanoparticle surface plasmon resonances have been extensively studied in the photoluminescence domain; little work however was devoted to electroluminescent and photovoltaic research. In this thesis, as a fundamental study we firstly investigated surface plasmon enhanced europium complex luminescence and obtained an improved understanding of the importance of optical spacer in metal enhanced fluorescence phenomenon. Under this guideline, we incorporated metal NPs into organic light emitting diodes (OLED) and organic solar cells, by means of thermal evaporation and wet chemistry. Metal nanoparticles are demonstrated to enhance the efficiency of both OLEDs and solar cells only under tailored device architecture. The surface plasmon enhanced local electric field plays an important and comprehensive role in enhancing device performance. In Alq3 based OLED we observed increased charge carrier injection by depositing Ag nanoparticles underneath the Al cathode; in Ir(ppy)3 based OLED we gained enhanced luminous efficiency via doping silica functionalized Ag nanoparticles into emitting layer; in P3HT based organic polymer solar cell we noticed an increased polymer absorption by incorporating Ag nanoparticles over the active layer. On the other hand, adverse effects such as metal nanoparticle induced charge carrier recombination and light extinction are also observed. The study of surface plasmon effects in organic optoelectronic devices reveals interesting surface plasmon features and permits to optimize optoelectronic devices from a novel point of view.