Modeling of GaInP/GaAs dual junction solar cells including tunnel junction

This paper presents research efforts conducted at the IES-UPM in the development of an accurate, physically-based solar cell model using the generalpurpose ATLASR device simulator by Silvaco. Unlike solar cell models based on a combination of discrete electrical components, this novel model extracts the electrical characteristics of a solar cell based on virtual fabrication of its physical structure, allowing for direct manipulation of materials, dimensions, and dopings. As single junction solar cells simulation was yet achieved, the next step towards advanced simulations of multi-junction cells (MJC) is the simulation of the tunnel diodes, which interconnect the subcells in a monolithic MJC. The first results simulating a Dual- Junction (DJ) GaInP/GaAs solar cells are shown in this paper including a complete Tunnel Junction (TJ) model and the resonant cavity effect occurring in the bottom cell. Simulation and experimental results were compared in order to test the accuracy of the models employed

Tunnel diode modeling, including nonlocal trap-assisted tunneling: A focus on III-V multijunction solar cell simulation

Multijunction solar cells (MJCs) based on III-V semiconductors constitute the state-of-the-art approach for high-efficiency solar energy conversion. These devices, consisting of a stack of various solar cells, are interconnected by tunnel diodes. Reliable simulations of the tunnel diode behavior are still a challenge for solar cell applications. In this paper, a complete description of the model implemented in Silvaco ATLAS is shown, demonstrating the importance of local and nonlocal trap-assisted tunneling. We also explain how the measured doping profile and the metalization-induced series resistance influence the behavior of the tunnel diodes. Finally, we detail the different components of the series resistance and show that this can help extract the experimental voltage drop experienced by an MJC due to the tunnel junction. The value of this intrinsic voltage is important for achieving high efficiencies at concentrations near 1000 suns

Distributed Simulation of Real Tunnel Junction Effects in Multi-Junction Solar Cells

In this paper, we present an improved 3D distributed model that considers real operation regimes in a tunnel junction. This advanced method is able to accurately simulate the high concentrations at which the current in the solar cell surpasses the peak current of the tunnel junction. Simulations of dual-junction solar cells were carried out with different light profiles and including chromatic aberration to show the capabilities of the model. Such simulations show that, under some circumstances, the solar cell short circuit current may be slightly higher than the tunnel junction peak current without showing the characteristic dip in the J-V curve. This behavior is caused by the lateral current spreading towards the dark regions, which occurs through the anode region of the tunnel junction

Silver Nanoparticles and PDMS Hybrid Nanostructure for Medical Applications

For many years, people have known about silver’s antibacterial qualities. Silver nanoparticles are widely used in consumer products, biomedical equipment, textile products and in other applications. Having a larger surface area to coat or spread over another surface, offers a greater contact area, therefore, increases antimicrobial properties. Also, these nanoparticles can be incorporated into polydimethylsiloxane (PDMS) implants as immobilized or occluded particles to improve their performance in the body. PDMS is commonly used for biomedical applications, including components for microfluidics, catheters, implants, valves, punctual plugs, orthopedics and micro gaskets. It can be manufactured easily in different forms such as fibers, fabrics, films, blocks and porous surfaces. The use of silver nanoparticles for their antimicrobial qualities improves PDMS biocompatibility, because it inhibits microbial growth, thereby making it more attractive for biomedical applications. The presence of metal nanoparticles also helps to reduce the hydrophobic nature of PDMS. This property of PDMS does not encourage cell adhesion, which is a very critical requirement for medical implants. Silver nanoparticles improve the silicone’s wettability. The exceptional properties of silver nanoparticles combined with the PDMS have made this hybrid nanostructure applicable to different medical uses

Extended description of tunnel junctions for distributed modeling of concentrator multi-junction solar cells

One of the key components of highly efficient multi-junction concentrator solar cells is the tunnel junction interconnection. In this paper, an improved 3D distributed model is presented that considers real operation regimes in a tunnel junction. This advanced model is able to accurately simulate the operation of the solar cell at high concentraions at which the photogenerated current surpasses the peak current of the tunnel junctionl Simulations of dual-junction solar cells were carried out with the improved model to illustrate its capabilities and the results have been correlated with experimental data reported in the literature. These simulations show that under certain circumstances, the solar cells short circuit current may be slightly higher than the tunnel junction peak current without showing the characteristic dip in the J-V curve. This behavior is caused by the lateral current spreading toward dark regions, which occurs through the anode/p-barrier of the tunnel junction

Influencia de las nanopartículas de sílice en polímeros termoplásticos

En este trabajo se prepararon sílices con distinto grado de hidrofilicidad para reducir el grado de interacción con el poliuretano y analizar la incidencia en las propiedades de los materiales compuestos obtenidos. Se incorporó una sílice pirogénica hidrófila a adhesivos de poliuretano con distinta relación NCO/OH donde el grado de separación de fases se vio favorecido en todos los poliuretanos, indicando una posible interacción de los grupos silanol de la sílice mediante enlaces de hidrógeno con el polímero. Por lo tanto, debería existir una variación de propiedades en los poliuretanos como respuesta a la presencia de la sílice dispersada.In this work we have prepared silicas with different hydrophilicity to reduce the degree of interaction with the polyurethane and analyze the effect on the properties of the composites obtained. A hydrophilic pyrogenic silica was incorporated in different polyurethane adhesives with different relation NCO/OH where the degree of phase separation is enhanced at all polyurethanes, indicating a potential interaction of the silanol groups of the silica by hydrogen bonding with the polymer. Therefore, there should be a variation in properties as polyurethanes response to the presence of the dispersed silica

Ampicillin-Loaded Chitosan Nanoparticles for In Vitro Antimicrobial Screening on Escherichia coli

Purpose: To develop ampicillin-loaded chitosan nanoparticles by modified ionic gelation method for evaluating their antimicrobial activity onto Escherichia coli

Estudio de las propiedades mecánicas de los perfiles de aluminio para la optimización del proceso de extrusión

Proyecto de Graduación (Licenciatura en Ingeniería en Materiales) Instituto Tecnológico de Costa Rica, Escuela de Ciencia e Ingeniería de los Materiales, 2007.El presente trabajo pertenece al Proyecto de Graduación que es requisito para optar por el grado de Licenciatura en la carrera de Ciencia e Ingeniería de Materiales, con énfasis en Procesos Industriales. Este se desarrolla en la planta de Extralum, Cartago. La planta de Extralum ubicada en Cartago se dedica a la fabricación de productos de aluminio para aplicaciones en puertas y ventanas. Actualmente, Extralum carece de un control sobre las propiedades mecánicas que presentan los productos de aluminio en función de los parámetros de velocidad y temperatura del proceso de extrusión. Para este proyecto se evaluaron las propiedades mecánicas del perfil designado como 1029, así como el tamaño de grano que presenta. El perfil 1029 presenta una aleación de aluminio 6063, el cual pasa por el tratamiento térmico denotado como T5. Se dieron recomendaciones para la corrección del proceso de extrusión, dando criterios basados en el análisis de las pruebas requeridas para este tipo de perfil. De la misma manera, a lo largo del proyecto se estudió el comportamiento de la aleación ante cambios de velocidad y temperatura durante el proceso de extrusión. Se determinaron las propiedades de resistencia máxima del perfil 1029, por medio del ensayo de tensión, las cuales cumplieron en un 100% con lo estipulado en la norma ASTM B557M. A su vez, se realizaron pruebas de dureza en los perfiles, las cuales, en un 93%, presentaron durezas superiores a 60 HBS, la cual es la dureza mínima requerida para una aleación 6063T5. También se determinó el tamaño de grano promedio ante las variaciones de temperatura y velocidad en el proceso de extrusión. El tamaño de grano encontrado en todas las muestras evidencia el descontrol sobre los parámetros de extrusión, ya que ninguno de estos se acercó al índice ASTM de tamaño de grano que se deseaba.Instituto Tecnológico de Costa Rica

Síntesis y caracterización de nanosílices funcionalizadas injertadas con 3-aminopropil trietoxisilano para ser utilizadas en adhesivos de poliuretano

En este trabajo se presentan los resultados obtenidos al modificar superficialmente una sílice pirogénica hidrófila comercial, con una superficie específica de 200 m2 /g, a la que se le injertó 3-aminopropiltrietoxisilano. La nanosílice modificada se añadió a adhesivos de poliuretano termoplástico en metiletilcetona. El material obtenido se caracterizó mediante sus propiedades mecánicas, térmicas, reológicas y adhesivas. Los resultados obtenidos se compararon con los de adhesivos de poliuretano sin sílice y con sílice sin modificar, preparados bajo las mismas condiciones experimentales.Fil: Vega Baudrit, José. Universidad Nacional. Escuela de Química. Laboratorio de Polímeros; Costa RicaFil: Sibaja Ballestero, María. Universidad Nacional. Escuela de Química. Laboratorio de Polímeros; Costa RicaFil: Martín Martinez, José Miguel. Universidad de Alicante. Departamento de Química Inorgánica. Laboratorio de Adhesión y Adhesivos; EspañaFil: Vazquez, Patricia Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentin