| A promising new technology for the 21st century is emerging based on molecular Organic Light Emitting Diodes (MOLEDs), incorporated in flat panel, full color and high resolution electronic displays. The goal of this doctoral thesis is to develop and spectroscopically study the properties of highly luminescent molecular composites, which are used as the emitting layer in MOLEDs. The molecular composite films, prepared by high vacuum deposition, consist of a highly fluorescent guest and a molecular organic host. The host has a dual nature: it is a carrier transporter and a light-emitter. The mechanisms leading to photo- and electroluminescence of guest molecules in organic matrices are also investigated, with the ultimate goal of developing an increased understanding of the migration of energy and generation of the emitted photon.; The third chapter focuses on optical and luminescence studies conducted on several molecular composites based on tris(8-hydroxyquinolinato) aluminum(III) (Alq3) as the host. An anthracene and naphthacene derivative, and two pyrromethene difluoroborate complexes were used as the highly fluorescent guest molecules. It is shown that doping Alq3 with a highly fluorescent molecule leads to a great enhancement of the luminescence quantum yield up to a value of virtually 100%.; The fourth chapter deals with an interesting family of highly fluorescent molecules based on quinacridone. They are photochemically stable and, have narrow spectra which lead to pure color output in display applications. The processes involved in generation of light by MOLEDs can be broken into the following steps: injection of charges (carriers) into the organic layer, transport of charges, recombination of carriers, exciton formation, exciton migration, emission of a photon and the fate of that photon within the device.; The fifth chapter investigates the emission mechanism of molecularly doped organic light-emitting diodes, where the emitting layer was composed of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1 '-biphenyl-4,4'-diamine (TPD) as the host and 5,6,11,12-tetraphenylnapthacene (rubrene) as the guest, in terms of energy transfer to and direct carrier recombination on the guest molecule. The dominant emission mechanism is attributed to the electron-hole recombination on rubrene molecules. (Abstract shortened by UMI.)... |
