Ingeniería molecular de materiales transportadores de huecos o electrones para células solares de perovskita

El desarrollo de alternativas limpias para remplazar las tecnologías actuales basadas en combustibles fósiles es de crucial importancia. Dentro de las tecnologías fotovoltaicas emergentes, las células solares basadas en perovskita (PSCs) han alcanzado eficiencias prometedoras. Objetivos Diseño, síntesis y caracterización de nuevos materiales transportadores de huecos (HTMs) con el fin de mejorar el rendimiento de PSCs. Estudio de la aplicación de una serie de derivados de C60 con diferente funcionalización química y energía del LUMO como materiales transportadores de electrones (ETMs) en PSCs invertidas. i) HTMs basados en tetraarileteno (TAE) y bifluorenilideno (BF) Nuevas moléculas basadas en TAE y BF como unidad central han sido diseñadas uniendo covalentemente diferentes fragmentos dadores de electrones. Son extremadamente baratos y de fácil preparación y han sido extensamente caracterizados, mostraron características prometedoras en PSCs. ii) HTMs basados en benzotritiofeno (BTT) y libres de azufre Se han sintetizado BTT1, BTT2 y BTT3, los cuales fueron obtenidos de manera satisfactoria a través de la unión del fragmento central BTT con diferentes unidades basadas en difenilamina. Alcanzaron valores de eficiencia (valores siempre en porcentaje) entre el 16 y el 18 en dispositivos basados en MAPbI3 y (FAPbI3)0.85(MAPbBr3)0.15. El efecto de la isomería, derivada de la posición de los átomos de azufre en el fragmento central, ha sido estudiado en las propiedades de BTT4 y BTT5. Valores extraordinarios de eficiencia del 19.0 y 18.2 han sido alcanzados como HTMs en células solares basadas en (FAPbI3)0.85(MAPbBr3)0.15. Se sintetizaron dos nuevas isoestructuras, con pirroles o anillos de furano fusionados a un anillo central de benzeno, BTP y BTF, respectivamente. Los extraordinarios valores de eficiencia alcanzados, son comparables a los obtenidos con spiroOMeTAD o BTT-3. iii) HTMs basados en tieno[3,2 b]tiofeno (TbT) Se empleó tienotiofeno como fragmento central en tres nuevos HTMs, unido covalentemente a unidades de p metoxidifenilamina a través de diferentes grupos espaciadores. Se obtuvieron valores de eficiencia de hasta 18.4 con TbT3 sin apenas histéresis. iv) C60 funcionalizados con ácido benzoico Derivados de C60, adecuadamente funcionalizados con ácido carboxílico fueron sintetizados. Concretamente, tres derivados de C60 fueron incorporados como interface en PSCs en forma de monocapa autoensamblada. En todos los casos, se observó una disminución en la histéresis. v) Diseño y síntesis de ThCBM ThCBM y ThCBM6 mostraron un comportamiento en dispositivos invertidos basados en perovskita similares a estudiado PCBM. Se presenta la síntesis del bisaducto de C60 que combina los fragmentos característicos del DPM6 y PCBM. Conclusiones El diseño de nuevos HTMs de bajo coste y fácil preparación ha permitido el estudio de la influencia de diferentes unidades dadoras de electrones, isomerización e incorporación de heteroátomos en el fragmento central para diseñar a la carta HTMs con propiedades moleculares favorables para su utilización en dispositivos fotovoltaicos basados en perovskita. De forma adicional, se ha realizado una estimación de su coste de preparación a escala de laboratorio, en torno a 50-80 US$ por gramo, muy competitivo en comparación con otros HTMs ya comercialmente disponibles. Estos costes de preparación, junto con los altos valores de eficiencia alcanzados en dispositivos fotovoltaicos, validan el potencial de los nuevos HTMs presentados en esta tesis, compitiendo favorablemente con spiroOMeTAD, en el mercado de las células solares basadas en pervoskita. Actualmente existe una solicitud de patente internacional pendiente de resolución final. Además, la preparación de los derivados de C60 presentados en esta tesis, ha permitido una notable mejora en dispositivos fotovoltaicos de configuración invertida

Analysis of the Hysteresis Behavior of Perovskite Solar Cells with Interfacial Fullerene Self-Assembled Monolayers

The use of self-assembled monolayers (SAMs) of fullerene derivatives reduces the hysteresis of perovskite solar cells (PSCs). We have investigated three different fullerene derivatives observing a decrease on hysteresis for all the cases. Several processes can contribute to the hysteresis behavior on PSCs. We have determined that the reduced hysteresis observed for devices with SAMs is produced by a decrease of the capacitive hysteresis. In addition, with an appropriated functionalization, SAMs can increase photocurrent even when no electron selective contact (ESC) is present and a SAM is deposited just on top of the transparent conductive oxide. Appropriated functionalization of the fullerene derivative, as introducing −CN groups, can enhance cell performance and reduce hysteresis. This work paves the way for a future enhancement of PSCs by a tailored design of the fullerene molecules that could actuate as an ESC by themselves

Spiro-derivatives as hole transporting materials for improving the performance of perovskite solar cells

The Sun is the most powerful source of energy in the Earth's solar system, which, in part, can be exploited by all the inhabitants of the Earth. The optimal exploitation of the fraction that arrives on earth is, undoubtedly, among the most important challenges nowadays of science. To convert sun light into chemical energy, the first silicon-based device Photovoltaic (PV) solar cells, prepared by Chapin in 1954 exhibiting an efficiency around 6% [1,2] used different semiconducting materials (inorganic, organic, molecular, polymeric, hybrids, quantum dots, etc.). Today the most promising technology to replace/complement crystalline silicon PV [3] are the Perovskites solar cells (PSCs) that emerged since 2009, achieving efficiencies of ~26 %. These results were obtained using commercially available spiro-OMeTAD as hole-transporting material (HTM) that are expensive materials due to its difficult purification and multi-step synthetic protocols (in harsh conditions) which limits its future use in large-scale applications. Considering the negative aspects related to the industrial production of the spiro-OMeTAD, we synthesized some intermediates necessary for the subsequent synthesis of four spiro-derivatives. Excellent results were obtained with some derivatives based on electron-rich spiranic scaffolds [4], synthesized by the Buchwald-Hartwig reaction, carried out in toluene. In this way it was possible to obtain the spiro-PTZ functionalized, by making structural modifications to the previously obtained derivatives, the yield of this synthesis was around 21%. The compounds obtained were incorporated into perovskite solar cells providing efficiencies higher than the standard used (spiroOMeTAD). The devices have been tested under illumination and have shown good stability over time

Cut or Burnt? – Categorizing morphological characteristics of heat-induced fractures and sharp force trauma

Distinguishing trauma from heat-induced fractures is a challenge faced by forensic anthropologists and pathologists during medicolegal investigations in which fire has been used by the perpetrators to destroy evidence. This paper aims to validate the provided identification features to distinguish between fire induced alterations and sharp force trauma. A total of 80 cremated adult individuals were used in this paper: 3 recently deceased embalmed cadavers from Cementerio Sur de Madrid for the sharp force trauma experiment in which 55 pre-burning injuries were inflicted using a machete and a serrated knife in different anatomical regions. And 77 cremated individuals from the Forensic Anthropology and Odontology Laboratory osteological collection. Five cremated long bones from this collection were selected, and 10 cuts were manually inflicted using a serrated knife to analyse post-burning trauma. Heat-induced changes and trauma morphologic characteristics were thus documented and analysed. The examination and documentation of morphological traits enabled the production of a heat-induced changes visual guide and a flow-chart. Two intraclass correlation tests were performed to validate the capacity of the observer to distinguish between fire related alterations and toolmarks. The results obtained in the statistical analysis indicate that, even if the toolmarks are visible and recognizable upon macroscopic observation by the observers, some features, such as the step and the transverse fractures can be mistaken with inflicted trauma. The use of the proposed features coupled with careful anthropological examination is recommended and has been found functional for participants with no prior knowledge in the analysis of cremated remains

Fashioning Fluorous Organic Spacers for Tunable and Stable Layered Hybrid Perovskites

Two dimensional (2D) organic-inorganic hybrid perovskites have recently attracted enormous attention due to their higher environmental stability with respect to three-dimensional (3D) perovskites and larger structural tunability. The layered structure relaxes constraints on the dimensions of the organic cations that alternate the inorganic sheets, opening up a large choice on the organics, ultimately enabling the creation of tunable layered perovskites. Here, we report on a series of fluorous cations, varying in size and shape, as building blocks for a new family of fluorous 2D lead-iodide perovskites. These display a large tunability in the optical and dielectric properties depending on the structure of the fluorous cations. Importantly, despite the invariant inorganic framework, the 2D perovskite electronic structure is strongly affected by the cation size. The longer the cation, the smaller the 2D perovskite band gap and the exciton binding energy (reducing from 400 meV down to 130 meV). Such variation is induced by the strain in the inorganic sheet, resulting in a more dispersed valence and conduction bands, in turn yielding a smaller band gap. In addition, a smaller effective mass for the 2D perovskite with the longest cation is calculated, for which improved transport properties are anticipated. Importantly, the fluorous moiety confers extreme stability to the 2D perovskite and enhances the hydrophobic character of the perovskite surface, which remains perfectly stable for more than one month in ambient conditions

Ingeniería Forestal y ambiental en medios insulares

Las Islas Canarias a pesar de su reducida extensión y del relativo poco peso específico a nivel mundial, no es ajena a los problemas globales detectados en la conservación de bosques y en la importancia que éstos tienen para obtener beneficios económicos, socioculturales y ambientales. La gestión forestal sostenible es en este sentido esencial para asegurar y compatibilizar los diversos beneficios del bosque. El papel específico de los bosques y su gestión son sin embargo temas aún por conocer en nuestras islas, por lo que el Año Internacional de los Bosques ha representado una oportunidad única para dar a conocer el mundo forestal y acercarlo a nuestra sociedad. El presente libro consta de 25 capítulos donde se ha contemplado la mayoría de los aspectos a tener en cuenta en la planificación y gestión del medio forestal y natural. Desde la historia forestal del archipiélago, hasta el uso y técnicas de manejo de los recursos naturales, incluyendo el agua, la energía en forma de biomasa y la selvicultura

Shift work and colorectal cancer risk in the MCC-Spain case-control study

Objectives Shift work that involves circadian disruption has been associated with a higher cancer risk. Most epidemiological studies to date have focused on breast cancer risk and evidence for other common tumors is limited. We evaluated the risk for colorectal cancer (CRC) in relation to shift work history in a population-based case-control study in Spain. Methods This analysis included 1626 incident CRC cases and 3378 randomly selected population controls of both sexes, enrolled in 11 regions of Spain. Sociodemographic and lifestyle information was assessed in face-to-face interviews. Shift work was assessed in detail throughout lifetime occupational history. We estimated the risk of colon and rectal cancer associated with rotating and permanent shift work (ever, cumulative duration, age of first exposure) using unconditional logistic regression analysis adjusting for potential confounders. Results Having ever performed rotating shift work (morning, evening and/or night) was associated with an increased risk for CRC [odds ratio (OR) 1.22, 95% confidence interval (95% CI) 1.04-1.43], as compared to day workers. Having ever worked permanent night shifts (?3 nights/month) was not associated with CRC risk (OR 0.79, 95% CI 0.62-1.00). OR increased with increasing lifetime cumulative duration of rotating shift work (P-value for trend 0.005) and were highest among subjects in the top quartiles of exposure (3 rdquartile, 20-34 years, OR 1.38, 95%CI 1.06-1.81; 4 thquartile, ?35 years, OR 1.36, 95% CI 1.02-1.79). Conclusions These data suggest that rotating shift work may increase the risk of CRC especially after long-term exposures

Entangled core/shell magnetic structure driven by surface magnetic symmetry-breaking in Cr2O3 nanoparticles

Bulk Cr2O3 is an antiferromagnetic (AFM) oxide that exhibits the magnetoelectric effect at room temperature, with neither spontaneous magnetization nor net electric polarization. These physical properties stem from a subtle competition between exchange and crystal field interactions. In this article, we exploit the symmetry breaking at the surface of Cr2O3 nanoparticles for unbalancing this delicate physical equilibrium. The emerging weak ferromagnetic signal we observe persists up to near room temperature (≈ 270 K) at which the antiferromagnetic order disappears. In addition, an exchange-bias effect, that rapidly decreases on heating from low temperature up to 30 K, is resistant to thermal disorder above 200 K. Our findings point to the possible formation of an entangled core/shell magnetic structure, where pinned uncompensated spins at the shell are randomly distributed in a low-temperature spin-glass ordering, with low net magnetic moment and an ordering temperature governed by the AFM Néel temperature.Work at University of Oviedo was financially supported by research projects MCIU-19-RTI2018-094683-B-C52 (MCIU/AEI/FEDER, UE) and AYUD/2021/51822 (FICyT, Principality of Asturias). Thanks are due to Elettra-Sincrotrone Trieste (Italy) and to Institut Laue-Langevin (France) for allocating beam time. We are grateful to the Scientific-Technical Services of the University Oviedo for providing assistance in transmission microscopy image acquisition and processing. Work at USF supported partially through US Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering under Award # DE-FG02-07ER46438. H. S. acknowledges support from the Bizkaia Talent Program, Basque Country (Spain). X. M. acknowledges support from the Grant Agency of the Czech Republic Grant no. 14-37427.Peer reviewe