Synthesis, characterization, and film fabrication of inorganic and hybrid semiconductor materials for optoelectonic applications:

We have developed and studied selected properties of a novel type of inorganic-organic hybrid semiconductor materials in order to enhance the functionality over their parent structures. Since inorganic organic hybrid semiconductor materials are composed of both inorganic and organic segments, one may expect them to have the advantage of combining the excellent electrical, optical, thermal and transport properties from the inorganic component with the flexibility, processability and structural diversity from the organic component. As a continuing effort, we have synthesized, modified, and characterized a number of selected structures with potential for solid state lighting applications. For example, we have developed the first inorganic organic semiconductor bulk material, double layered 2D-Cd2Q2(ba)(Q=S, Se), capable of producing direct white light. This type of materials could be promising for use as a single-material white-light-emitting source in white LEDs. Luminescence properties of these hybrid semiconductors can be tuned systematically by changing their composition and doping level. In addition, a thin pellet of one of our hybrid semiconductor materials without any modifications showed low electrical conductivity. Significant improvement may be anticipated with modifications. Solution processed deposition techniques provide great opportunities for optical and optoelectronic devices, such as displays, solid state lighting, and solar cells, because it enables to fabricate flexible devices with low-cost and large area fabrications. Most semiconductors show very low solubility in organic solvents, thus limiting the opportunities to prepare thin films using soluble precursors. In this study, we have developed a simple, efficient, and low-cost solution-processed deposition route to fabricate metal chalcogenide semiconductor thin films by using soluble precursors via a spin-coating technique. Surface morphology was directly influenced by the choice of organic solvents as well as the spin-coating sequences, thus affecting the electrical transport of the films. In the case of hybrid semiconductors, a conducting polymer was employed to help forming more uniform composite films.Ph.D.Includes bibliographical referencesby Wooseok K