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 872
Full-Wafer Roller-NIL Processes for Silicon Solar Cell Texturisation - Hauser, Hubert; Michl, B.; Walk, C.; Eisenlohr, Johannes; Benick, Jan; Mellor Null, Alexander Virgil; Muller, Claas; Hermle, Martin; Bläsi, Benedikt
The highest solar cell efficiencies both for c-Si and mc-Si were reached using template based texturing processes. Especially for mc-Si the benefit of a defined texture, the so called honeycomb texture, was demonstrated impressively. However, up until now, no industrially feasible process has been available to pattern the necessary etching masks with the sufficient resolution. Roller-Nanoimprint Lithography (Roller-NIL) has the potential to overcome these limitations and to allow high quality pattern transfers, even in the sub-micron regime, in continuous in-line processes. Therefore, this etch-mask patterning technique is a suitable solution to bring such elaborate features like the honeycomb texture to...
IBPOWER Project, Intermediate band materials and solar cells for photovoltaics with high efficiency and reduced cost - Martí Vega, Antonio; Antolín Fernández, Elisa; García-Linares Fontes, Pablo; Cánovas Díaz, Enrique; Fuertes Marrón, David; Tablero Crespo, César; Mendes, Manuel J.; Mellor Null, Alexander Virgil; Tobías Galicia, Ignacio; Levy, M.Y.; Hernández Martín, Estela; Luque López, Antonio; Farmer, C.D.; Stanley, Colin; Campion, Richard P.; Hall, J.L.; Novikov, S.V.; Foxon, C.T.; Scheer, Roland; Marsen, Bjorn; Schock, Hans Werner; Picault, Michel; Chaix, Caterine
IBPOWER is a Project awarded under the 7th European Framework Programme that aims to advance research on intermediate band solar cells (IBSCs). These are solar cells conceived to absorb below bandgap energy photons by means of an electronic energy band that is located within the semiconductor bandgap, whilst producing photocurrent with output voltage still limited by the total semiconductor bandgap. IBPOWER employs two basic strategies for implementing the IBSC concept. The first is based on the use of quantum dots, the IB arising from the confined energy levels of the electrons in the dots. Quantum dots have led to devices...
TCAD for PV: a fast method for accurately modelling metal impurity evolution during solar cell processing - Powell, Douglas Michael; Fenning, David P.; Hofstetter, Jasmin; Lelievre, Jean Francoise; Cañizo Nadal, Carlos del; Buonassisi, Tonio
Coupled device and process silumation tools, collectively known as technology computer-aided design (TCAD), have been used in the integrated circuit industry for over 30 years. These tools allow researchers to quickly converge on optimized devide designs and manufacturing processes with minimal experimental expenditures. The PV industry has been slower to adopt these tools, but is quickly developing competency in using them. This paper introduces a predictive defect engineering paradigm and simulation tool, while demonstrating its effectiveness at increasing the performance and throughput of current industrial processes. the impurity-to-efficiency (I2E) simulator is a coupled process and device simulation tool that links...
Electrical, photoelectrical and morphological properties of ZnO nanowire networks grown on SiO2 and on Si - Celeste Vega, Nadia; Tirado, Mónica; Comedi, David; Rodríguez Domínguez, Andrés; Rodríguez Rodríguez, Tomás; Hughes, Gareth M.; Grovenor, Chris R.M.; Audebert, Fernando
ZnO nanofibre networks (NFNs) were grown by vapour transport method on Si-based substrates. One type of substrate was SiO2 thermally grown on Si and another consisted of a Si wafer onto which Si nanowires (NWs) had been grown having Au nanoparticles catalysts. The ZnO-NFN morphology was observed by scanning electron microscopy on samples grown at 600 °C and 720 °C substrate temperature, while an focused ion beam was used to study the ZnO NFN/Si NWs/Si and ZnO NFN/SiO2 interfaces. Photoluminescence, electrical conductance and photoconductance of ZnO-NFN was studied for the sample grown on SiO2. The photoluminescence spectra show strong peaks...
The unstoppable rise of photovoltaic solar energy: PV vs. PV - Luque López, Antonio
Photovoltaic (PV) solar energy has been growing during the last decade an explosive rate. Last year (2011) the solar cell production amounted to more than 37 GW. It is the energy technology most installed nowadays. The power generated by the 37 GW is similar to the one generated by about 7 nuclear units of 1 GW each. The solar industry is already a huge industry dominated by Asian countries led by China. It is not anymore a promise. It is just a reality.
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...