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With their simple fabrication, narrow light spectrum, and color tunability, a class of materials known as perovskites are emerging as promising candidates for light emission applications. These materials, when exposed to normal atmospheric conditions show significant degradation. Improved protection has been demonstrated by embedding perovskites in polymers. Furthermore, the addition of a surfactant into the precursor solution has been shown to increase stability and allow for color tuning by exploiting quantum confinement effects. However, the effects of surfactants typically used to stabilize perovskites in solution have not been explored in this polymer embedding strategy. Here we determine the physical and optical emission changes produced by modifying the concentration of octylamine, butylamine, and oleylamine in the perovskite precursor solution prior to embedding into a polystyrene substrate. Using optical emission spectroscopy, we measure emission spectra of perovskite nanocrystals embedded in the polymer. Changes in morphology and dispersion of the perovskite particles within the polymer are observed using UV illuminated optical microscopy. XRD data suggests increased crystallinity with the addition of short chain surfactant. Our measurements in emission show that the location of the emission peak and overall shape of the emission spectra change when longer chain surfactant is added while short chain surfactant reduces nanorod formation without a significant change in particle dispersion or emission. The work suggests that increased long chain surfactant concentration prohibits perovskite crystal growth within the polymer leading to increased optical transparency and quantum confinement effects observable through photo luminescent emission.

The rapid advancement of portable and wearable technologies has challenged research to improve upon current renewable battery energy storage systems. By using nanotechnology, it is now possible to access more of the energy storage theoretical values that have been unattainable thus far. We have developed a method to create freestanding holey thin films through combinations of electrochemical and chemical vapor deposition (CVD) techniques to be used in renewable energy storage systems. Freestanding thin films promote excellent contact between the residual conductive framework and any functionalized active component specific to the designed material. Without requiring any other additives, the as-prepared freestanding thin films can be mechanically and chemically tuned to allow for use in a wide range of applications. Incorporation of micro- and nano-sized holey structures dramatically enhances the electrochemically active surface area, which is essential for facilitating appropriate reactions in conversion type energy storage systems. Combining the freestanding and holey components with an active layer effectively enhances conductivity and reduces the electron transfer distance at the electrode-electrolyte interface. Herein, two separately designed freestanding holey thin films were successfully used as cathode materials for lithium-sulfur battery (Li-S) and magnesium-ion battery (MIB) energy storage systems.

Quantum Cascade Lasers have recently gained considerable attention for their capability to emit infrared radiation in a broad infrared spectral region, very compact dimensions, and high optical power/efficiency. Increasing continuous wave optical power is one of the main research directions in the field. A straightforward approach to increasing optical power in the pulsed regime is to increase number of stages in the cascade structure. However, due to a low active region thermal conductivity, the increase in number of stages leads to active region overheating in continuous wave operation. In this work, an alternative approach to power scaling with device dimensions is explored: number of stages is reduced to reduce active region thermal resistance, while active region lateral size is increased for reaching high optical power level. Using this approach, power scaling for active region width increase from 10µm to 20µm is demonstrated for the first time. An analysis based on a simple semi-empirical model suggests that laser power can be significantly improved by increasing characteristic temperature T0 that describes temperature dependence of laser threshold current density.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references. Also available in electronic version.

Thesis(Ph.D.)--Case Western Reserve University, 2009 / Abstract Department of Chemical Engineering Title from OhioLINK (viewed on 20 April 2009) Available online via the OhioLINK ETD Center

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xxvi, 214 p.; also includes graphics (some col.) Includes bibliographical references (p. 203-214). Available online via OhioLINK's ETD Center

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (Ph.D.)--Washington State University. / Includes bibliographical references.