RUI: Investigation of Electron Migration and Trapping in Doped Luminescent Materials

Central Washington University, Ellensburg WA

Investigators

Abstract

Technical Description: This research project involves the study of electron-hole (e-h) pair transport and trapping processes in solid-state luminescent materials under vacuum ultraviolet excitation. These materials are comprised of an oxide host and a rare-earth dopant. Under vacuum ultraviolet excitation, an e-h pair is created in the host that must migrate and be trapped by the dopant for luminescence to occur. The research project addresses two fundamental questions: (1) How is the efficiency of e-h transfer affected by the position of dopant states relative to host band states? (2) How much does the choice of dopant influence the degree of surface loss observed in particles with sizes of from 50 to 500 nanometers? This is accomplished through systematic spectroscopic investigations of materials of controlled particle size, and the evaluation of these data in the context of current models. The analysis and modeling of these experimental data allow for the assessment of the mobility of e-h pairs in a given host, as well as the degree to which absorbed energy is lost to bulk defects versus surface traps. Such a differentiation is especially important to the development of efficient nanoscale optical materials that have an intrinsically high surface area. The project also applies these methods to larger bandgap phosphate hosts. Non-technical Description: The objective of this research is to understand the fundamental structure/property relationships that govern the efficiency of solid-state luminescent materials, especially materials with sub-micrometer particle sizes, under vacuum ultraviolet excitation. Such materials often exhibit properties different from their bulk counterparts, and can improve the performance of certain technologies such as in high-definition displays. The PI has established a rigorous research program in solid-state chemistry at Central Washington University, with undergraduate students comprising the bulk of the investigative team. Students are gaining a deeper and broader scientific training, which serves as excellent preparation for graduate school or future professional endeavors. Undergraduate students trained in the PI's lab often published papers in peer-reviewed journals and routinely go on to pursue graduate degrees.