Archivo Digital UPM
This is an institutional repository providing access to the research output of the institution. Primarily contains thesis.
Materia = Electrónica
Mostrando recursos 301 - 320 de 868
In situ control of Si(100) and Ge(100) surface preparation for the heteroepitaxy of III-V solar cell architectures - Brückner, Sebastian; Supplie, Oliver; Barrigón Montañés, Enrique; Dobrich, Anja; Luczak, Johannes; Löbbel, Claas; Rey-Stolle Prado, Ignacio; Kleinschmidt, Peter; Döscher, Henning; Hannappel, Thomas
Si(100) and Ge(100) substrates essential for subsequent III-V integration were studied in the hydrogen ambient of a metalorganic vapor phase epitaxy reactor. Reflectance anisotropy spectroscopy (RAS) enabled us to distinguish characteristic configurations of vicinal Si(100) in situ: covered with oxide, cleaned by thermal removing in H2, and terminated with monohydrides when cooling in H2 ambient. RAS measurements during cooling in H2 ambient after the oxide removal process revealed a transition from the clean to the monohydride terminated Si(100) surface dependent on process temperature. For vicinal Ge(100) we observed a characteristic RA spectrum after annealing and cooling in H2 ambient. According...
Indoor characterization at production sccale: 200 kWp of CPV solar simulator measurements - Ferrer Rodríguez, Juan Pablo; Martínez, María; Trujillo Serrano, Pablo Jesús; Rubio, Francisca; Askins, Stephen; Domínguez Domínguez, César; Herrero Martin, Rebeca; Sala Pano, Gabriel
In order to complement ISFOC’s characterization capabilities, a Helios 3198 CPV Solar Simulator was installed in summer 2010. This Solar Simulator, based on a parabolic mirror and a high-intensity, small area Xenon flash lamp was developed by the Instituto de Energía Solar in Madrid  and is manufactured and distributed by Soldaduras Avanzadas . This simulator is used not only for R&D purposes, but as a quality control tool for incoming modules that are to be installed in ISFOC’s CPV plants. In this paper we will discuss the results of recent measurements of close to 5000 modules, the entire production...
CPV hybrid system in ISFOC building, first results - Trujillo Serrano, Pablo Jesús; Alamillo, César; Gil Murillo, Eduardo; Rubia, Oscar de la; Martínez, María; Rubio, Francisca; Cadavid, Andros; Navarro, José; Hillenbrand, Sascha; Ballesteros Sánchez, Isabel; Castillo Cagigal, Manuel; Masa Bote, Daniel; Matallanas de Avila, Eduardo; Caamaño Martín, Estefanía; Gutiérrez Martín, Álvaro
PV Off-Grid systems have demonstrated to be a good solution for the electrification of remote areas . A hybrid system is one kind of these systems. The principal characteristic is that it uses PV as the main generator and has a backup power supply, like a diesel generator, for instance, that is used when the CPV generation is not enough to meet demand. To study the use of CPV in these systems, ISFOC has installed a demonstration hybrid system at its headquarters. This hybrid system uses CPV technology as main generator and the utility grid as the backup generator. A...
Progress on the development of a technology for silicon purification - Cañizo Nadal, Carlos del; Méndez Giménez, L.; Ramos Cabal, Alba; Rodríguez Rodríguez, Araceli
The polysilicon market is experiencing tremendous changes due to the strong demand from Photovoltaics (PV), which has by far surpassed the demand from Microelectronics. The need of solar silicon has induced a large increase in capacity, which has now given a scenario of oversupply, reducing the polysilicon price to levels that put a strong pressure on the cost structure of the producers. The paper reports on the R&D efforts carried out in the field of solar silicon purification via the chlorosilane route by a private-public consortium that is building a pilot plant of 50-100 tonnes/year, that will synthesize trichlorosilane, purify...
Progress on optimization of the solar cell fabrication process by impurity-to-efficiency predictive simulator - Peral Boiza, Ana; Cañizo Nadal, Carlos del; Luque López, Antonio
To optimize the last high temperature step of a standard solar cell fabrication process (the contact cofiring step), the aluminium gettering is incorporated in the Impurity-to-Efficiency simulation tool, so that it models the phosphorus and aluminium co-gettering effect on iron impurities. The impact of iron on the cell efficiency will depend on the balance between precipitate dissolution and gettering. Gettering efficiency is similar in a wide range of peak temperatures (600-850 ºC), so that this peak temperature can be optimized favoring other parameters (e.g. ohmic contact). An industrial co-firing step can enhance the co-gettering effect by adding a temperature plateau...
Surface Impedance Characterization for Mutual Coupling Calculation of Patches on a Dielectric-Coated PEC Circular Cylinder - García Aguilar, Andrés; Sipus, Zvonimir; Sierra Pérez, Manuel
A novel formulation for the surface impedance characterization is introduced for the canonical problem of surface fields on a perfect electric conductor (PEC) circular cylinder with a dielectric coating due to a electric current source using the Uniform Theory of Diffraction (UTD) with an Impedance Boundary Condition (IBC). The approach is based on a TE/TM assumption of the surface fields from the original problem. Where this surface impedance fails, an optimization is performed to minimize the error in the SD Green?s function between the original problem and the equivalent one with the IBC. This asymptotic method, accurate for large separations...
Surface Impedance Characterization for UTD Based Solution with IBC for Surface Fields on a Dielectric-Coated PEC Circular Cylinder - García Aguilar, Andrés; Sipus, Zvonimir; Sierra Pérez, Manuel
A novel formulation for the surface impedance characterization is introduced for the canonical problem of surface fields on a perfect electric conductor (PEC) circular cylinder with a dielectric coating due to a electric current source using the Uniform Theory of Diffraction (UTD) with an Impedance Boundary Condition (IBC). The approach is based on a TE/TM assumption of the surface fields from the original problem. Where this surface impedance fails, an optimization is performed to minimize the error in the SD Green?s function between the original problem and the equivalent one with the IBC. This new approach requires small changes in...
BatNet: a 6LoWPAN-based sensors and actuators network - Campo Jimenez, G.; Montoya Marina, Eduardo; Martin Perandones, Jorge; Gómez Gil de San Vicente, Igor; Santamaria Galdon, Maria Asuncion
Improving energy efficiency in buildings is one of the goals of the Smart City initiatives and a challenge for the European Union. This paper presents a 6LoWPAN wireless transducer network (BatNet) as part of an open energy management system. This network has been designed to operate in buildings, to collect environmental information (temperature, humidity, illumination and presence) and electrical consumption in real time (voltage, current and power factor). The system has been implemented and tested in the Energy Efficiency Research Facility at CeDInt-UPM.
Open multi-technology building energy management system - Caffarel Rodriguez, Jaime; Campo Jimenez, G.; Martin Perandones, Jorge; Gómez Otero, César; Martinez García, Rocío; Santamaria Galdon, Maria Asuncion
Energy Efficiency is one of the goals of the Smart Building initiatives. This paper presents an Open Energy Management System which consists of an ontology-based multi-technology platform and a wireless transducer network using 6LoWPAN communication technology. The system allows the integration of several building automation protocols and eases the development of different kind of services to make use of them. The system has been implemented and tested in the Energy Efficiency Research Facility at CeDInt-UPM.
Atlas-free Brain Tissue Segmentation Using a Single T1-weighted MRI Acquisition - Kober, Tobias; Roche, Alexis; Esteban Sanz-Dranguet, Oscar; Gorthi, Subrahmanyam; Rives, Delphine; Bach-Cuadra, Meritxell; Meuli, Reto; Krueger, Gunnar
Many studies investigating the aging brain or disease-induced brain alterations rely on accurate and reproducible brain tissue segmentation. Being a preliminary processing step prior to the segmentation, reliableskull-stripping the removal ofnon-brain tissue is also crucial for all later image assessment. Typically, segmentation algorithms rely on an atlas i.e. pre-segmented template data. Brain morphology, however, differs considerably depending on age, sex and race. In addition, diseased brains may deviate significantly from the atlas information typically gained from healthy volunteers. The imposed prior atlas information can thus lead to degradation of segmentation results. The recently introduced MP2RAGE sequence provides a bias-free T1...
Estructura electrónica de fotocatalizadores compuestos ZnO-TiO2 - Conesa, Jose Carlos
Recientes publicaciones han mostrado propiedades fotocatalíticas interesantes en sistemas basados en TiO2 y ZnO. En unos casos hay presentes fases de ambos óxidos binarios en íntimo contacto  y en otros se tienen óxidos mixtos (titanatos de Zn) de distintas estequiometrías ; estos últimos, además, se han podido dopar con nitrógeno para obtener actividad con luz visible . Las características electrónicas relevantes de estos sistemas (posición relativa de los niveles de ambas fases en el primero, estructura de bandas para los titanatos con o sin N) se conocen muy poco. Aquí se realiza un estudio teórico cuántico de estos materiales,...
Study of the Electrical Behavior in Intermediate Band-Si Junctions - Pastor Pastor, David; Olea Ariza, Javier; Prado Millán, Alvaro del; García Hemme, Eric; García Hernansanz, Rodrigo; González Pariente, L.; Mártil de la Plaza, Ignacio; González Díaz, Germán
In this study we analyze the electrical behavior of a junction formed by an ultraheavily Ti implanted Si layer processed by a Pulsed Laser Melting (PLM) and the non implanted Si substrate. This electrical behavior exhibits an electrical decoupling effect in this bilayer that we have associated to an Intermediate Band (IB) formation in the Ti supersaturated Si layer. Time-of-flight secondary ion mass spectrometry (ToFSIMS) measurements show a Ti depth profile with concentrations well above the theoretical limit required to the IB formation. Sheet resistance and Hall mobility measurements in the van der Pauw configuration of these bilayers exhibit a...
Effect of concentration on the performance of quantum dot intermediate-band solar cells - Okada, Y.; Yoshida, Katsuhisa; Shoji, Y.; Ogura , A.; García-Linares Fontes, Pablo; Martí Vega, Antonio; Luque López, Antonio
Implementation of a high-efficiency quantum dot intermediate-band solar cell (QD-IBSC) must accompany a sufficient photocurrent generation via IB states. The demonstration of a QD-IBSC is presently undergoing two stages. The first is to develop a technology to fabricate high-density QD stacks or a superlattice of low defect density placed within the active region of a p-i-n SC, and the second is to realize half-filled IB states to maximize the photocurrent generation by two-step absorption of sub-bandgap photons. For this, we have investigated the effect of light concentration on the characteristics of QDSCs comprised of multi-layer stacks of self-organized InAs/GaNAs QDs...
NGCPV: A new generation of concentrator photovoltaic cells, modules and systems - Cristóbal López, Ana Belén; Martí Vega, Antonio; Sala Pano, Gabriel; Bett, Andreas W.; Ekins-Daukes, Ned; Roca, Franco; Luque Heredia, Ignacio; Warmuth, Werner; Merten, Jens; Okada, Y.; Hishikawa, Y.; Takamoto, Tatsuya; Araki, Kenji; Fukuyama, A.; Kuze, N.; Kita, T.; Kotagiri, Akira; Yamaguchi, M.; Luque López, Antonio
This work introduces the lines of research that the NGCPV project is pursuing and some of the first results obtained. Sponsored by the European Commission under the 7th Framework Program and NEDO (Japan) within the first collaborative call launched by both Bodies in the field of energy, NGCPV project aims at approaching the cost of the photovoltaic kWh to competitive prices in the framework of high concentration photovoltaics (CPV) by exploring the development and assessment of concentrator photovoltaic solar cells and modules, novel materials and new solar cell structures as well as methods and procedures to standardize measurement technology for...
Nano-imprinted rear-side diffraction gratings for absorption enhancement in solar cells - Mellor Null, Alexander Virgil; Hauser, Hubert; Guttowski, Aron; Wellens, Christine; Bläsi, Benedikt; Tobías Galicia, Ignacio; Martí Vega, Antonio; Luque López, Antonio
As wafer-based solar cells become thinner, light-trapping textures for absorption enhancement will gain in importance. In this work, crystalline silicon wafers were textured with wavelength-scale diffraction grating surface textures by nanoimprint lithography using interference lithography as a mastering technology. This technique allows fine-tailored nanostructures to be realized on large areas with high throughput. Solar cell precursors were fabricated, with the surface textures on the rear side, for optical absorption measurements. Large absorption enhancements are observed in the wavelength range in which the silicon wafer absorbs weakly. It is shown experimentally that bi-periodic crossed gratings perform better than uni-periodic linear gratings....
Guide to intermediate band solar cell research - Martí Vega, Antonio; Antolín Fernández, Elisa; García-Linares Fontes, Pablo; Hernández Martín, Estela; Ramiro Gonzalez, Iñigo; Moura Dias Mendes, Manuel Joao de; Mellor Null, Alexander Virgil; Artacho Huertas, Irene; López Estrada, Esther; Tobías Galicia, Ignacio; Fuertes Marrón, David; Tablero Crespo, César; Cristóbal López, Ana Belén; Luque López, Antonio
The intermediate band solar cell (IBSC) is a solar cell that, in order to increase its efficiency over that of single gap solar cells, takes advantage of the absorption of below-bandgap energy photons by means of an intermediate band (IB) located in the semiconductor bandgap. For this process to improve the solar cell performance, the belowbandgap photon absorption has to be effective and the IB cannot limit the open-circuit voltage of the cell. In this paper we provide a guide to the new researcher interested in the idea in order he can quickly become familiar with the concept and updated...
Sulfuros fotocatalizadores que utilizan ampliamente el espectro de luz visible - Conesa, Jose Carlos; Lucena, Raquel; Fresno, Fernando; Wahnón Benarroch, Perla; Palacios Clemente, Pablo; Seminóvski Pérez, Yohanna
Cuando se usa fotocatálisis, tanto para procesos de descontaminación como para síntesis química específica y (especialmente) para aprovechamiento de energía solar, importa aprovechar un rango muy amplio de luz visible. Para ello se estudian hoy principalmente óxidos (con o sin adición de aniones que disminuyen el gap como el nitrógeno); los sulfuros, como el bien conocido CdS, tienen estabilidad limitada, sobre todo para procesos de fotooxidación en presencia de agua en los que sufren corrosión. Aquí se presentan estudios sobre sulfuros como el In2S3 y el SnS2 (con bandgaps respectivos de 2.0 y 2.2 eV ) cuyos metales tienen mayor...
Novel Gravity Distortion Evaluation on Large
Antenna Array for Deep Space Communication - Salas Natera, Miguel Alejandro; Martínez Rodríguez-Osorio, Ramón; Haro Ariet, Leandro de; Calvo Ramón, Miguel
This paper presents a simple gravity evaluation model for large reflector antennas and the experimental example for a case study of one uplink array of 4x35-m antennas at X and Ka band. This model can be used to evaluate the gain reduction as a function of the maximum gravity distortion, and also to specify this at system designer level. The case study consists of one array of 35-m antennas for deep space missions. Main issues due to the gravity effect have been explored with Monte Carlo based simulation analysis.