| A number of materials exist for organic light-emitting diodes (OLEDs). These include small molecules and conjugated polymers. Small molecules can be precisely identified and purified but typically require vapor depositon and have a tendency towards microcrystallinity. Conjugated polymers can be easily and cheaply deposited by spin-casting or printing from solution, however they are difficult to obtain in strict purity resulting in inconsistent properties. Furthermore, many OLEDs require the use of multi-layers for sufficient efficiency.; This dissertation describes a number of strategies to obtain materials with the attributes of both small molecules and conjugated polymers while avoiding drawbacks such as microcrystallinity. In addition these materials are designed for use as the single layer in an OLED. This dissertation begins by describing sate-of-the-art methods for OLED fabrication and measurement. The rest describes the design, synthesis, and characterization of a number of well-defined, small molecules and intermediate-sized macromolecules.; One class of molecules has four conjugated oligomers attached to a carbon atom providing a tetrahedral shape that discourages crystallization in thin films. Films are characterized by atomic force microscopy (AFM), fluorescence microscopy, and are compared to OLED performance as a function of casting solvent and heat treatment.; Another class of molecules uses small molecules blended into conjugated polymers thereby taking advantage of the electrical properties of the polymer (host) and the emission properties of the small molecule (guest). For example, lanthanides blended into conjugated polymers give a narrow emission spectra. Both red (612 nm) and infrared (1100 nm, 1540 nm) emission can be obtained in this manner. By insulating the guest from the host using by adding tert-butyl groups, reduced charge trapping is acheived. By blending iridium complexes designed to be miscible with conjugated polymer hosts through the incorporation of oligofluorene groups into polyfluorene and polyvinylcarbazole, highly efficieny OLEDs are realized by utilizing all of the charges via charge trapping and triplet harvesting.; One molecule is modularly designed to have a phenanthroline ligand for good electron transport, and a lignand with a carbazole fragment and alkoxy groups for hole transport and good film forming properties, respectively. This molecules is used as the single component in an OLED. |
