Síntesis y caracterización de nano- y microestructuras basadas en SnO₂ y Li₂SnO₃ con aplicaciones en dispositivos ópticos y células solares híbridas

En esta memoria de tesis doctoral se exponen y discuten los resultados más relevantes de la investigación llevada a cabo sobre el crecimiento, caracterización y aplicaciones de nano- y microestructuras de SnO2 dopado con Cr, de Li2SnO3 y láminas delgadas de materiales compuestos híbridos con matriz polimérica conductora (PEDOT:PSS) y nanoestructuras de SnO2 (nanohilos o nanopartículas) como relleno. A lo largo de este trabajo se han estudiado posibles aplicaciones de las nano- y microestructuras crecidas en resonadores ópticos, guías de luz, dispositivos emisores de luz y células solares híbridas. El SnO2 es un óxido semiconductor ampliamente utilizado en diversas aplicaciones, debido a sus atractivas propiedades físico-químicas, entre las que destacan aplicaciones en sensado de gases, catálisis, como electrodos transparentes y aplicaciones en energía. La aplicabilidad del SnO2 puede ampliarse a través del control de diversos parámetros tales como el tamaño, la morfología y el dopado. Por su parte, el Li2SnO3 es utilizado en diversas aplicaciones entre las que destaca la fabricación de electrodos para baterías de tipo ion-Li, si bien también se usa en otras aplicaciones de catálisis y en la fabricación de materiales dieléctricos que operen a frecuencias en el rango de las microondas. El Li2SnO3 a pesar de ser utilizado frecuentemente en diversas aplicaciones es un material poco estudiado del que aún se desconocen muchas de sus propiedades físicas..

The Role of Underlayers and Overlayers in Thin Film BiVO4 Photoanodes for Solar Water Splitting

This is the pre-peer reviewed version of the following article: The Role of Underlayers and Overlayers in Thin Film BiVO4 Photoanodes for Solar Water Splitting, which has been published in final form at https://doi.org/10.1002/admi.201900299. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.Light‐driven water splitting with metal oxide semiconductor materials to produce H2 constitutes one of the most promising energy conversion technologies built on solar power. BiVO4 stands out as one of the most attractive metal oxides with reported photocurrents close to its theoretical maximum of 7.5 mA cm−2 at 1 sun illumination. The present work addresses the state‐of‐the‐art strategies to enhance the performance of this material for water oxidation by heterostructuring with different underlayer (SnO2 and WO3) and overlayer (NiOOH/FeOOH, Co–Pi, Co–Fe Prussian Blue derivative) materials, with particular emphasis on the physico‐chemical mechanisms responsible for the reported enhancements

Li2SnO3 branched nano- and microstructures with intense and broadband white-light emission

Exploiting the synergy between microstructure, morphology and dimensions by suitable nanomaterial engineering, can effectively upgrade the physical properties and material performances. Li2SnO3 elongated nano- and microstructures in form of belts, wires, rods and branched structures have been fabricated by a vapor-solid method at temperatures ranging from 700 to 900 °C using metallic Sn and Li2CO3 as precursors. The achievement of these new morphologies can face challenging applications for Li2SnO3, not only in the field of energy storage, but also as building blocks in optoelectronic devices. The micro- and nanostructures grown at 700 and 800 °C correspond to monoclinic Li2SnO3, while at 900 °C complex Li2SnO3/SnO2 core-shell microstructures are grown, as confirmed by X-ray diffraction and Raman spectroscopy. Transmission electron microscopy reveals structural disorder related to stacking faults in some of the branched structures, which is associated with the presence of the low-temperature phase of Li2SnO3. The luminescent response of these structures is dominated by intense emissions at 2, 2.5 and 3 eV, almost completely covering the whole range of the visible light spectrum. As a result, white-light emission is obtained without the need of phosphors or complex quantum well heterostructures. Enhanced functionality in applications such as in light-emitting devices could be exploited based on the high luminescence intensity observed in some of the analysed Li2SnO3 structures

New Views on Carrier Diffusion and Recombination by Combining Small Perturbation Techniques: Application to BiVO4 Photoelectrodes

Impedance spectroscopy (IS), intensity-modulated photocurrent spectroscopy (IMPS), and intensity-modulated photovoltage spectroscopy (IMVS) are well-established powerful modulated techniques to characterize optoelectronic devices. Their combined use has proven to provide an understanding of the behavior and performance of these systems, far beyond the output obtained from their independent analysis. However, this combination is shown to be challenging when applied to complex systems. Herein, IS, IMPS, and IMVS are cooperatively used, for the first time, to study the distributed photogeneration, diffusion, and recombination processes in a photoanode of zircon-doped bismuth vanadate. The use of this methodology reveals that the carriers that determine the response of the device are the electrons when the device is illuminated from the hole-collector side (electrolyte) and the holes when the illumination reaches the device from the electron-collector side. Detailed quantitative information is obtained for each carrier, including recombination lifetime, diffusion coefficient and collectrion and separation efficiencies, identifying the latter as the main limitation of this device. This methodology is a powerful tool that can be used for the characterization and understanding of the operating processes of other photoconversion devices.Funding for open access charge: CRUE-Universitat Jaume

Intensity-Modulated Photocurrent Spectroscopy for Solar Energy Conversion Devices: What Does a Negative Value Mean?

Small perturbation techniques constitute a wide family of tools for the characterization of solar energy conversion devices such as photovoltaic cells and photoelectrochemical (PEC) cells for solar fuel production. Two main small perturbation methods frequently used in the area of solar energy conversion materials are impedance spectroscopy (IS) and intensity-modulated photocurrent spectroscopy (IMPS). The first one consists of applying a small voltage perturbation and measuring modulated extracted current. The second one consists of applying the perturbation to the illumination and measuring the modulated extracted current

CLN3 loss disturbs membrane microdomain properties and protein transport in brain endothelial cells

Juvenile neuronal ceroid lipofuscinosis (JNCL) is a fatal childhood-onset neurodegenerative disorder caused by mutations in ceroid lipofuscinosis neuronal-3 (CLN3), a hydrophobic transmembrane protein of unresolved function. Previous studies indicate blood–brain barrier (BBB) defects in JNCL, and our earlier report showed prominent Cln3 expression in mouse brain endothelium. Here we find that CLN3 is necessary for normal trafficking of the microdomain-associated proteins caveolin-1, syntaxin-6, and multidrug resistance protein 1 (MDR1) in brain endothelial cells. Correspondingly, CLN3-null cells have reduced caveolae, and impaired caveolae- and MDR1-related functions including endocytosis, drug efflux, and cell volume regulation. We also detected an abnormal blood–brain barrier response to osmotic stress in vivo. Evaluation of the plasma membrane with fluorescent sphingolipid probes suggests

Photochromic mechanism in oxygen-containing yttrium hydride thin films: An optical perspective

Oxygen-containing yttrium hydride thin films exhibit photochromic behavior: Transparent thin films reversibly switch from a transparent state to a photodarkened state after being illuminated with UV or blue light. From optical spectrophotometry and ellipsometry measurements of the transparent state and photodarkened state, it is concluded that the photochromic effect can be explained by the gradual growth, under illumination, of metallic domains within the initial wide-band-gap semiconducting lattice. This conclusion is supported by Raman measurements