Synthetic strategies for shape control and tunable doping of colloidal zinc oxide nanocrystals
- Zinc oxide (ZnO) is a wide-band gap II-VI semiconductor with various optoelectronic applications owing to its transparency to visible light and tunable optical/electronic properties achieved by doping. In this dissertation, a modular synthetic design approach is presented that overcomes many of the synthetic challenges associated with zinc oxide nanorods and enables nearly independent control of morphology and impurity incorporation. Manipulation of alcoholysis reaction kinetics through multiple precursor solution injections and judicious use of phosphonic acid surfactants enables the synthesis of nanorods with highly tunable shapes, lengths (40-200 nm), diameters (6-80nm), and doping levels (with aluminum and indium cations).Subsequently, this dissertation focuses on strategies to simultaneously control the shape and doping level of zinc oxide nanorods. The increased stability of dopant precursors, limited solid-state diffusion in ZnO nanocrystals, and unintentional dopant-induced shape effects make it extremely difficult to control both shape and doping in anisotropic zinc oxide nanorods. Here, we show that growth of an undoped ZnO shell incorporates surface segregated dopants on ZnO nanorods with high (> 50%) efficiency and preserves nearly the entire nanorod morphology. Both nanorod shape and dopant incorporation are achieved through kinetic control of reaction conditions. The structural and optoelectronic effects of dopant incorporation in these nanorods are characterized and discussed with an emphasis on near-infrared plasmonic applications. Finally, solution processing of ZnO nanocrystals into nanostructured films via spray deposition is explored as a low-cost, scalable method for improved optical performance in photovoltaic devices. Spray deposited nanostructured ZnO films fabricated form precursor nanoparticle inks exhibit highly tunable light scattering properties. Integration of spray-deposited ZnO films into GaAs photovoltaics results in increased short-circuit currents and efficiencies owing to the texture-induced absorption and anti-reflective properties of the nanostructured ZnO films.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Stanford University, Department of Materials Science and Engineering.
|Brongersma, Mark L
|Brongersma, Mark L
|Statement of responsibility
|Submitted to the Department of Materials Science and Engineering.
|Thesis (Ph.D.)--Stanford University, 2014.
- © 2014 by Saahil Mehra
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