Study and characterization of the ZnPc:C60/MoOx interface in organic solar cells by means of photoelectron spectroscopy

Dissertation to obtain the academic degree of Master in materials engineering submitted to the Faculty of science and engineering of Universidade Nova de LisboaThe search for low cost photovoltaics has led to the use of organic materials as possible candidates to substitute silicon based solar devices. Organic materials have high absorption coe cients, allowing the use of very thin lms and low cost solution phase manufacturing techniques. Control over the electronic structure of organic/inorganic semiconductor interfaces is a key step for the development of these devices. In the present study this issue is addressed for an organic solar cell with an inverted structure: an organic absorber layer of zinc phthalocyanine: Fullerene heterojuntion, sandwiched between a front electrode of zinc oxide doped with aluminium, an intermediate bu er layer of molybdenum oxide and a silver electrode. The objective of this experimental work has been the investigation of the electronic properties of the MoOx/ZnPc:C60 interface. For this purpose photoelectron spectroscopy using di erent types of radiation has been carried out. Results will be presented on the interface analysis carried out by ultraviolet photoelectron spectroscopy (UPS) for the study of the valence electron levels and by X-ray photoelectron spectroscopy (XPS) to probe the core electron levels. Valence band o sets and work function values at MoOx/ZnPc:C60 interfaces have been characterized as a function of MoOx thickness and as a function of annealing temperature. Current-voltage characteristics (I-V) were measured as a function of annealing temperature and the optical properties of the MoOx layer were measured by transmission in the range 250-2500 nm. Near edge X-ray absorption ne structure (NEXAFS)spectroscopy was used to give additional insight into the situation of the electronic structure: spectra were taken from the electron storage ring for synchrotron radiation (BESSY II, Berlin)

Novel electron acceptors and new solution processed hole blocking layer for organic solar cells

La utilització de materials orgànics per a la fabricació de cèl·lules solars és una de les alternatives considerades actualment per a reduir els costos de fabricació de sistemes fotovoltaics. Els materials orgànics tenen coeficients d’absorció elevats que permeten la utilització de capes primes i tècniques de fabricació de baix cost. L’objectiu d’aquesta tesi ha estat contribuir a la millora de les cèl·lules solars orgàniques d’heterounió massiva, mitjançant la incorporació de nous materials acceptors i donadors d’electrons, així com de capes de blocatge de forats depositades a partir de solucions. S’ha dut a terme l’estudi dels efectes de les capes transportadores d’electrons i forats en termes d’eficiència i de degradació dels dispositius fotovoltaics. S’han estudiat i fabricat capes de blocatge de forats amb bathocuproïna (BCP) depositada a través d’una tecnologia de solucions com a substitució del calci.El empleo de materiales orgánicos en la fabricación de celulas solares es una de las alternativas actualmente consideradas para reducir los costes de fabricación de los sistemas fotovoltaicos. Los materiales organicos tienen coeficientes de absorpción elevados, permitiendo el uso de capas finas y técnicas de fabricación de bajo coste. El objectivo de esta tesis ha sido contribuir en la mejora de las células solares orgánicas de heterounión masiva, mediante la incorporación de nuevos materiales aceptores de la familia de los PDI, y de capas bloqueadoras de huecos depositadas a partir de soluciones. Se han estudiado los efectos de las capas transportadoras de electrones y huecos en términos de eficiencia y degradación de dispositivos fotovoltaicos. Se han fabricado capas bloqueadoras de huecos con bathocuproine (BCP) depositada a través de una tecnología de soluciones como sustituyente del Calcio. Se han estudiato y caracterizado las propriedades morfologicas y optoelectronicas de celulas solares con las estructuras ITO/PEDOT:PSS/PTB7:PDI/Ca/Ag y ITO/PEDOT:PSS/PTB7:PCBM/BCP/Ag. Se ha llevado a cabo una caracterización de las propiedades morfológicas y fotofísicas de los dispositivos fotovoltaicos fabricados a través de varios métodos de investigación, entre los cuales medidas J-V, EQE, Difracción de rayos X, medidas espectroscopia UV-Vis, medidas de movilidad de portadores, medidas de extracción de carga y foto-voltaje transitorio, AFM y medidas de ángulo de contacto.The search for low cost photovoltaics has led to the use of organic materials as possible candidates to substitute silicon based solar devices. Organic materials have high absorption coefficients, allowing the use of thin layers and low cost solution phase manufacturing techniques. The objective of this thesis has been to contribute to the improvement of bulk-heterojunction organic solar cells through the incorporation of new acceptor materials of the PDI family and of a film layer of Bathocuproine (BCP) as hole blocking layer. The BCP layer was spin coated from a dilute toluene/methanol solution directly on top of the active layer. The morphological, optoelectronic properties of solar cells with the following structures have been studied and characterized: ITO / PEDOT: PSS / PTB7: PDI / Ca / Ag and ITO / PEDOT: PSS / PTB7: PCBM / BCP / Ag. For this purpose various characterization methods has been carried out, including JV measurements, EQE, X-ray diffraction, UV-Vis spectroscopy, carrier mobility measurements , charge extraction and transient photo-voltage measurements and AFM

Targeting cancer addiction for SALL4 by shifting its transcriptome with a pharmacologic peptide

Sal-like 4 (SALL4) is a nuclear factor central to the maintenance of stem cell pluripotency and is a key component in hepatocellular carcinoma, a malignancy with no effective treatment. In cancer cells, SALL4 associates with nucleosome remodeling deacetylase (NuRD) to silence tumor-suppressor genes, such as PTEN. Here, we determined the crystal structure of an amino-terminal peptide of SALL4(1-12) complexed to RBBp4, the chaperone subunit of NuRD, at 2.7 Å, and subsequent design of a potent therapeutic SALL4 peptide (FFW) capable of antagonizing the SALL4-NURD interaction using systematic truncation and amino acid substitution studies. FFW peptide disruption of the SALL4-NuRD complex resulted in unidirectional up-regulation of transcripts, turning SALL4 from a dual transcription repressor-activator mode to singular transcription activator mode. We demonstrate that FFW has a target affinity of 23 nM, and displays significant antitumor effects, inhibiting tumor growth by 85% in xenograft mouse models. Using transcriptome and survival analysis, we discovered that the peptide inhibits the transcription-repressor function of SALL4 and causes massive up-regulation of transcripts that are beneficial to patient survival. This study supports the SALL4-NuRD complex as a drug target and FFW as a viable drug candidate, showcasing an effective strategy to accurately target oncogenes previously considered undruggable

A Rational Approach Towards a New Ferrocenyl Pyrrolidine for Stereoselective Enamine Catalysis

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Characterization of the histone methyltransferase PRDM9 using biochemical, biophysical and chemical biology techniques

PRDM proteins have emerged as important regulators of disease and developmental processes. To gain insight into the mechanistic actions of the PRDM family, we have performed comprehensive characterization of a prototype member protein, the histone methyltransferase PRDM9, using biochemical, biophysical and chemical biology techniques. In the present paper we report the first known molecular characterization of a PRDM9-methylated recombinant histone octamer and the identification of new histone substrates for the enzyme. A single C321P mutant of the PR/SET domain was demonstrated to significantly weaken PRDM9 activity. Additionally, we have optimized a robust biochemical assay amenable to high-throughput screening to facilitate the generation of small-molecule chemical probes for this protein family. The present study has provided valuable insight into the enzymology of an intrinsically active PRDM protein

Sfere, spazio, suono. Il pensiero mediologico di Peter Sloterdijk.

La tesi sviluppa un percorso attraverso il pensiero mediologico di Peter Sloterdijk in Sphere I, Blasen, con particolare interesse all'origine del suo discorso sul suono e sul fenomeno musicale, alla luce dei saggi di estetica musicali che hanno costellato la sua ricerca dalle origini fino ai tempi più recenti

Determinación de la función de almacenamiento a nivel de celda para su utilización en la modelación matemática del escurrimiento superficial

Se presenta una metodología para la obtención de la función de almacenamiento y conducción (FAC) a nivel de celda para un modelo matemático distribuido, cuasi-bidimensional basado en esquemas de celdas. La FAC resulta determinante en el proceso de transformación lluvia-caudal y de propagación de crecidas en modelos físicamente basados y para la obtención de variables de flujo (alturas de agua y velocidades). En una primera etapa se realiza la comparación entre las curvas de distribución de frecuencia acumulada adimensionalizada de altura vs. área superficial obtenidas mediante relevamientos topográficos de detalle (a nivel de subcelda) y obtenidas mediante el modelo digital del terreno para la discretización adoptada (ventana de 3 x 3 celdas del modelo). Se observa un adecuado grado de similitud entre los dos niveles de detalle por lo que en la segunda etapa se realiza la obtención de los parámetros de la ecuación utilizada que vincula altura vs. área superficial; lo que permite obtener la FAC en cada celda del modelo. La metodología permite incorporar la variabilidad espacial de la FAC en todo el dominio espacial de modelación. En investigaciones futuras se incorporará la FAC en cada celda; se simularán eventos observados y se compararán los resultados.Fil: Stenta, Hernán R. Departamento de Hidráulica – Escuela de Ingeniería Civil (FCEIA – Universidad Nacional de Rosario) y Centro Universitario Rosario de Investigaciones Hidroambientales (FCEIA – Universidad Nacional de Rosario), Rosario, Argentina.Fil: Riccardi, Gerardo A. Departamento de Hidráulica – Escuela de Ingeniería Civil (FCEIA – Universidad Nacional de Rosario) y Centro Universitario Rosario de Investigaciones Hidroambientales (FCEIA – Universidad Nacional de Rosario) y Consejo de Investigaciones de la Universidad Nacional de Rosario, Rosario, Argentina.Fil: Basile, Pedro A. Departamento de Hidráulica – Escuela de Ingeniería Civil (FCEIA – Universidad Nacional de Rosario) y Centro Universitario Rosario de Investigaciones Hidroambientales (FCEIA – Universidad Nacional de Rosario), Rosario, Argentina

TAL Effectors Specificity Stems from Negative Discrimination

Transcription Activator-Like (TAL) effectors are DNA-binding proteins secreted by phytopathogenic bacteria that interfere with native cellular functions by binding to plant DNA promoters. The key element of their architecture is a domain of tandem-repeats with almost identical sequences. Most of the polymorphism is located at two consecutive amino acids termed Repeat Variable Diresidue (RVD). The discovery of a direct link between the RVD composition and the targeted nucleotide allowed the design of TAL-derived DNA-binding tools with programmable specificities that revolutionized the field of genome engineering. Despite structural data, the molecular origins of this specificity as well as the recognition mechanism have remained unclear. Molecular simulations of the recent crystal structures suggest that most of the protein-DNA binding energy originates from non-specific interactions between the DNA backbone and non-variable residues, while RVDs contributions are negligible. Based on dynamical and energetic considerations we postulate that, while the first RVD residue promotes helix breaks - allowing folding of TAL as a DNA-wrapping super-helix - the second provides specificity through a negative discrimination of matches. Furthermore, we propose a simple pharmacophore-like model for the rationalization of RVD-DNA interactions and the interpretation of experimental findings concerning shared affinities and binding efficiencies. The explanatory paradigm presented herein provides a better comprehension of this elegant architecture and we hope will allow for improved designs of TAL-derived biotechnological tools

Diphenylphenoxy-Thiophene-PDI Dimers as Acceptors for OPV Applications with Open Circuit Voltage Approaching 1 Volt

Two new perylenediimides (PDIs) have been developed for use as electron acceptors in solution-processed bulk heterojunction solar cells. The compounds were designed to exhibit maximal solubility in organic solvents, and reduced aggregation in the solid state. In order to achieve this, diphenylphenoxy groups were used to functionalize a monomeric PDI core, and two PDI dimers were bridged with either one or two thiophene units. In photovoltaic devices prepared using PDI dimers and a monomer in conjunction with PTB7, it was found that the formation of crystalline domains in either the acceptor or donor was completely suppressed. Atomic force microscopy, X-ray diffraction, charge carrier mobility measurements and recombination kinetics studies all suggest that the lack of crystallinity in the active layer induces a significant drop in electron mobility. Significant surface recombination losses associated with a lack of segregation in the material were also identified as a significant loss mechanism. Finally, the monomeric PDI was found to have sub-optimum LUMO energy matching the cathode contact, thus limiting charge carrier extraction. Despite these setbacks, all PDIs produced high open circuit voltages, reaching almost 1 V in one particular caseThis work was supported by the Spanish Ministry of Economy, Industry and Competitiveness (MEIC) (TEC2015-71324-R, CTQ2014-55798-R and TEC2015-71915-REDT (MINECO/FEDER))This work was supported by the Catalan Institution for Research and Advanced Studies (ICREA) (ICREA “Academia Award”, AGAUR 2017 SGR 017SGR1527