Diseño de la absorción y emisión ópticas de nanomateriales en entornos fotónicos controlados

El trabajo descrito en esta memoria es el resultado de cuatro años de investigación en el Instituto de Ciencia de Materiales de Sevilla bajo la dirección del Prof. Hernán Míguez y el Dr. Juan F. Galisteo-López y versa sobre el control de la absorción y emisión ópticas de nanomateriales integrados en entornos fotónicos controlados Tras un revisión del estado del arte y una introducción general a las estructuras fotónicas empleadas en este estudio (Cap. 1), se describen en detalle cada una de las herramientas utilizadas en la realización de esta tesis (Cap. 2), desde la simulación hasta la caracterización de los distintos materiales estudiados. En primer lugar se describen los métodos teóricos y en segundo lugar se hace una descripción completa de los métodos experimentales, incluyendo tanto fabricación como caracterización óptica de las distintas estructuras realizadas. En el Cap. 3 se presenta una aproximación para modificar de forma controlada la absorción óptica de nanopartículas metálicas integradas en resonadores ópticos unidimensionales. Se detalla cómo incorporar nanopartículas metálicas de tamaño y forma arbitrarios en las estructuras fotónicas así como la caracterización óptica del conjunto y se explican teóricamente los resultados obtenidos. En el Cap. 4 se demuestra la posibilidad de emplear métodos de procesado en solución para controlar de forma determinista la emisión de nanoemisores integrándolos en el interior de resonadores ópticos unidimensionales. Se detalla cómo integrar nanoesferas emisoras con un control nanométrico de su posición en el interior de la estructura fotónica así como la caracterización óptica del conjunto y la reproducción teórica de las modificaciones obtenidas. Además, se diseñan, fabrican y caracterizan estructuras tipo resonador óptico que integran nanosheets y nanoemisores como material base para el desarrollo de nuevos sensores fluorescentes de humedad. En el Cap. 5 se presenta una aproximación para maximizar la potencia radiada por una monocapa de nanoemisores integrada en cristales fotónicos unidimensionales auto-soportados acoplados de manera conformal a superficies metálicas de distinta composición y geometría. Se demuestra la versatilidad de estas estructuras híbridas, dieléctricas-metálicas, mediante el diseño, fabricación y caracterización de sistemas emisores cuasi-monocromáticos, direccionales o auto-focalizados. En los Apen. A y Apen. B se presentan resultados derivados de algunas de las herramientas desarrolladas durante el transcurso de esta tesis. Estos resultados muestran el uso de estructuras híbridas metal-dieléctrico basadas en metales de bajo coste como espejos solares de alta reflectancia y el diseño y fabricación de módulos fotovoltaicos que combinan un concentrador solar luminiscente y cristales fotónicos unidimensionales, respectivamente. Por último, en el Apen. C se presenta la aproximación numérica, basada en el método de las diferencias finitas en el dominio del tiempo, mediante la cual se obtiene información sobre la potencia extraída a través de la superficie de estructuras tipo multicapa que integran fuentes de luz nanométricas.Premio Extraordinario de Doctorado U

Absorption enhancement in methylammonium lead iodide perovskite solar cells with embedded arrays of dielectric particles

In the field of hybrid organic-inorganic perovskite based photovoltaics, there is a growing interest in the exploration of novel and smarter ways to improve the cells light harvesting efficiency at targeted wavelength ranges within the minimum volume possible, as well as in the development of colored and/or semitransparent devices that could pave the way both to their architectonic integration and to their use in the flowering field of tandem solar cells. The work herein presented targets these different goals by means of the theoretical optimization of the optical design of standard opaque and semitransparent perovskite solar cells. In order to do so, we focus on the effect of harmless, compatible and commercially available dielectric inclusions within the absorbing material, methylammonium lead iodide (MAPI). Following a gradual and systematic process of analysis, we are capable of identifying the appearance of collective and hybrid (both localized and extended) photonic resonances which allow to significantly improve light harvesting and thus the overall efficiency of the standard device by above 10% with respect to the reference value while keeping the semiconductor film thickness to a minimum. We believe our results will be particularly relevant in the promising field of perovskite solar cell based tandem photovoltaic devices, which has posed new challenges to the solar energy community in order to maximize the performance of semitransparent cells, but also for applications focusing on architectonic integration.European Union 307081Ministerio de Economía y Competitividad MAT2014-54852-R, MAT2017-88584-

Plasmonic Nanoparticles as Light-Harvesting Enhancers in Perovskite Solar Cells: A User’s Guide

In this Perspective we discuss the implications of employing metal particles of different shape, size, and composition as absorption enhancers in methylammonium lead iodide perovskite solar cells, with the aim of establishing some guidelines for the future development of plasmonic resonance-based photovoltaic devices. Hybrid perovskites present an extraordinarily high absorption coefficient which, as we show here, makes it difficult to extrapolate concepts and designs that are applied to other solution-processed photovoltaic materials. In addition, the variability of the optical constants attained from perovskite films of seemingly similar composition further complicates the analysis. We demonstrate that, by means of rigorous design, it is possible to provide a realistic prediction of the magnitude of the absorption enhancement that can be reached for perovskite films embedding metal particles. On the basis of this, we foresee that localized surface plasmon effects will provide a means to attain highly efficient perovskite solar cells using films that are thinner than those usually employed, hence facilitating collection of photocarriers and significantly reducing the amount of potentially toxic lead present in the device.European Union 307081Ministerio de Economía y Competitividad MAT2011-23593, MAT2014-54852-

16 Years (2006–2021) of Surface Ozone Measurements in Córdoba (Southern Spain): Trends and the Impact of the COVID-19 Lockdown

Surface ozone concentrations (O3) during the period 2006–2021 are analysed at Córdoba city (southern Iberian Peninsula) in suburban and urban sampling sites. The aims are to present the levels and temporal variations, to explore trends and to quantity the variation in O3 concentrations in the context of the COVID-19 lockdown. The O3 means are higher in the suburban station (62 µg m−3 and 51.3 µg m−3), being the information level threshold only exceeded twice during this period. The daily evolution shows a maximum at about 17:00 UTC, whereas the minimum is reached at about 9:00 UTC, with higher levels in the suburban station. The seasonal evolution of this daily cycle also presents monthly differences in shape and intensity between stations. The trends are analysed by means of daily averages and daily 5th and 95th percentiles, and they show a similar increase in all of these parameters, with special emphasis on the daily P95 concentrations, with 0.27 µg m−3 year−1 and 0.24 µg m−3 year−1. Finally, the impact of the COVID-19 lockdown shows a decline in O3 concentrations over 10%

Modeling weakly scattering random media: a tool to resolve the internal structure of nanoporous materials

Nanoporous media scatter a small fraction of the light propagating through them, even if pore sizes are significantly smaller than the characteristic visible wavelengths. The disordered spatial modulation of the refractive index at the few or few tens of nanometers length scale, resulting from the presence of randomly distributed air bubbles or solid aggregates within a continuous solid background, gives rise to these weak scattering effects. However, standard theoretical approaches to describe this kind of media use effective medium approximations that do not account for diffuse, ballistic, and specular components. Herein, all spectral components and the angular distribution of the scattered light are captured through optical modeling. A Monte Carlo approach, combining scattering Mie theory and Fresnel equations, implemented within a genetic algorithm, allows us to decode the void and aggregate size distribution and hence the internal structure of a nanocrystalline titania (TiO2) film chosen as a paradigmatic example. The approach allows to generically describe the scattering properties of nanoporous materials which, as shown herein, may be used to decipher their internal structure from the fitting of their far-optical field propertiesFinancial support of the Spanish Ministry of Science and Innovation under grant PID2020-116593RB-I00, funded by MCIN/AEI/10.13039/501100011033, and of the Junta de Andalucía under grant P18-RT-2291 (FEDER/UE), is gratefully acknowledged. A.J.-S. gratefully acknowledges Spanish Ministry of Universities for funding through a Beatriz Galindo Research fellowship BG20/0001

Maximized performance of dye solar cells on plastic: a combined theoretical and experimental optimization approach

We demonstrate that a combined optimization approach based on the sequential alternation of theoretical analysis and experimental realization gives rise to plastic supported dye solar cells for which both light harvesting efficiency and electron collection are maximized. Rationalized configurations with optimized light trapping and charge extraction are realized to achieve photoanodes on plastic prepared at low temperature, showing a power conversion efficiency of 8.55% and a short circuit photocurrent of 16.11 mA cm 2, unprecedented for plastic based dye solar cell devices. Furthermore, the corresponding fully flexible designs present stable mechanical properties after several bending cycles, displaying 7.79% power conversion efficiency, an average broadband internal quantum efficiency above 90%, and a short circuit photocurrent of 15.94 mA cm 2, which is the largest reported value for bendable cells of this sort to dateEuropean Union 307081, 622533Ministerio de Economía y Competitividad MAT2014-54852-R, MAT2011–2359

Finite Size Effects on Light Propagation throughout Random Media: Relation between Optical Properties and Scattering Event Statistics

This work introduces a thorough analysis of light transport in thin optically disordered media. The diffusive properties of a turbid material are generally dictated by the transport mean free path, lt. For depths larger than this characteristic length, light propagation can be considered fully randomized. There is however a range of thicknesses for which light becomes only partly randomized, as it only undergoes a single or very few scattering events. The effects of such finitude are experimentally and theoretically studied on the optical properties of the material, such as the angular distribution of scattered light. Simulations provide insight into the phenomena that occur within the optically disordered slab, like the number of scattering events that photons undergo during propagation throughout the material, as a function of the built-in wavelength dependent scattering mean free path, lsc. This approach provides fundamental information about photon transport in finite optically random media, which can be put into practice to design diffusers with specific requirements in terms of the spectral and angular properties of the scattered light.Spanish Ministry of Economy and Competitiveness MAT2017-88584-REuropean Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme NANOPHOM 71583

La ley de reciprocidad cuadrática y sus generalizaciones

La motivación del presente documento reside en dar luz a la ley de reciprocidad cuadrática, también conocida como ``aureum theorema" \ o teorema áureo por Gauss. Esta ley se presenta como uno de los objetos de estudio clásicos de la teoría de números. De hecho, la ley de reciprocidad cuadrática es un teorema sobre aritmética modular que da condiciones para la solubilidad de ecuaciones cuadráticas módulo un número primo p.<br /

Infrared-excess white dwarfs in the Gaia 100 pc sample

We analyse the 100¿pc Gaia white dwarf volume-limited sample by means of VOSA (Virtual Observatory SED Analyser) with the aim of identifying candidates for displaying infrared excesses. Our search focuses on the study of the spectral energy distribution (SED) of 3733 white dwarfs with reliable infrared photometry and GBP - GRP colours below 0.8 mag, a sample that seems to be nearly representative of the overall white dwarf population. Our search results in 77 selected candidates, 52 of which are new identifications. For each target, we apply a two-component SED fitting implemented in VOSA to derive the effective temperatures of both the white dwarf and the object causing the excess. We calculate a fraction of infrared-excess white dwarfs due to the presence of a circumstellar disc of 1.6 ± 0.2 per¿cent, a value that increases to 2.6 ± 0.3 per¿cent if we take into account incompleteness issues. Our results are in agreement with the drop in the percentage of infrared excess detections for cool (20¿000¿K) white dwarfs obtained in previous analyses. The fraction of white dwarfs with brown dwarf companions we derive is ¿0.1–0.2 per¿cent.Peer ReviewedPostprint (author's final draft

CONSTRUCCIÓN GEOGRÁFICA DE LA PROVINCIA DE LIMÓN, COSTA RICA: PODER, CULTURA Y TERRITORIO

A territorial analysis of Limón Province is made through a critical perspective of how this region was conceived and built throughout its history. We discuss about some geographical constructions and imaginaries made towards Limón from the capital, by reviewing a series of Costa Rican Geographies, books that have been used for education and knowledge of Costa Rican territory. An alternative way of interpreting Limón Province is presented, based on its culturally diverse territory and its possibilities.En este artículo se realiza un análisis territorial de Limón a través de una crítica hacia los proyectos que han sido plasmados en el territorio y la forma como éste ha sido concebido. Además, se reflexiona sobre algunas construcciones geográficas elaboradas desde relaciones de poder hacia la provincia Limón, esto por medio de la revisión de una serie de Geografías de Costa Rica, libros que han sido utilizados para la educación y el conocimiento del territorio costarricense. A la vez se presenta una forma alternativa de interpretar a esta región, como un territorio cultural diverso