Impact of metal-organic vapor phase epitaxy environment on silicon bulk lifetime for III–V-on-Si multijunction solar cells

With the final goal of integrating III-V materials on silicon substrates for tandem solar cells, the influence of the Metal-Organic Vapor Phase Epitaxy (MOVPE) environment on the minority carrier properties of silicon wafers has been evaluated. These properties will essentially determine the photovoltaic performance of the bottom cell in a III-V-on-Si tandem solar cell. A comparison of the base minority carrier lifetimes obtained for different thermal processes carried out in a MOVPE reactor on Czochralski silicon wafers has been carried out. An important degradation of minority carrier lifetime during the surface preparation (i.e. H2 anneal) has been observed. Three different mechanisms have been proposed for explaining this behavior: 1) the introduction of extrinsic impurities coming from the reactor; 2) the activation of intrinsic lifetime killing impurities coming from the wafer itself; and finally, 3) the formation of crystal defects, which eventually become recombination centers. The effect of the emitter formation by phosphorus diffusion has also been evaluated. In this sense, it has been reported that lifetime can be recovered during the emitter formation either by the effect of the P on extracting impurities, or by the role of the atomic hydrogen on passivating the defects

Efectos de un programa basado en tecnologías de información y comunicación sobre el rendimiento académico en matemática en alumnos de tercero de secundaria de la Institución Educativa Nº 6093, UGEL 01 – 2011

El propósito de este estudio fue evaluar los efectos de un programa basado en tecnologías de información y comunicación sobre el rendimiento académico del área de matemática en los alumnos del tercero de secundaria de la institución educativa Nº 6093-UGEL 01. El diseño de la investigación utilizado fue cuasi-experimental. La muestra estuvo constituida por un grupo de control de 30 estudiantes y un grupo experimental de 30 estudiantes. El instrumento de recolección de datos utilizado fue una prueba de matemáticas, que fue aplicada antes y después de la aplicación del programa. Los hallazgos indicaron que el grupo experimental obtuvo un aprendizaje significativo como efecto de la aplicación del programa, debido a que se hallaron diferencias significativas (p < .001) en los puntajes de rendimiento en la prueba de matemáticas, entre el grupo experimental y el control; además las mediciones pre y post-test del grupo experimental también mostraron diferencias significativas (p < .001)

Investigacion sobre secado natural y solar de trozos de yuca con aire forzado con un ventilador

The natural and solar drying system of cassava chips using natural air forced through the product with the help of a fan is described. This process enables drying to occur in the least time possible without affecting chip quality; likewise, it is not expensive. The system consists of a rural drying bin, a fan, and a solar collector which is optional depending on the drying capacity of the natural air. Illustrations are provided of the system; tables included indicate the materials required and the costs of constructing the different components of the system. The costs of different attachments are also indicated as well as labor requirements. (CIAT

Status of Ultra-High Concentrator Multijunction Solar Cell Development at IES-UPM.

After the successful implementation of a record performing dual-junction solar cell at ultra high concentration, in this paper we present the optimization of key aspects in the transition to a triple-junction device, namely the hetero nucleation of III-V structures onto germanium substrates. This optimization is based on in-situ RAS measurements during the MOVPE growth of the triple-junction solar cell structure and subsequent AFM analysis. The correlation between RAS and AFM allows detecting which RAS features correlate with good morphology and low RMS roughness. TEM analysis confirms that the quality of the triple-junction structures grown is good, revealing no trace of antiphase disorder, and showing flat, sharp and clear interfaces. Triple-junction solar cells manufactured on these structures have shown a peak efficiency of 36.2% at 700X, maintaining an efficiency over 35% from 300 to 1200 suns

Assessment of rear-surface processing strategies for III-V on Si multijunction solar cells based on numerical simulations

The manufacturing of high-efficiency III-V on Si multijunction solar cells needs the development of hybrid, i.e., adapted to both families of materials, solar cell processing techniques, able to extract the full photovoltaic potential of both the subcells. This fact especially impacts the processing of the silicon rear surface of the tandem, which cannot receive treatments commonly used in the single-junction Si solar cell industry [Al-back surface field (BSF), thermal SiO2, and so on], since these would result in an excessive thermal load that would deteriorate the III-V upper layers (top cell, tunnel junction, and buffer layer). However, the Si bottom cell requires an advanced design with good rear passivation, a good ohmic contact, and good carrier selectivity, so that its contribution to the efficiency of the tandem is maximized. Accordingly, in this paper, several low-temperature compatible rear-surface passivation techniques for the Si bottom subcell in a monolithic III-V/Si tandem solar cell are explored. In particular, aluminum BSFs, passivated emitter and rear cell (PERC)-like architecture, passivated emitter and rear locally diffused (PERL)-like architecture formed with low thermal loads, and heterojunction with intrinsic thin layer (HIT)-like processes are assessed using numerical simulations, and a comparison of the Si bottom cell performance for the mentioned alternatives in a GaAsP/Si dual-junction solar cell is presented

Optimizing diffusion, morphology and minority carrier lifetime in silicon for GaAsP/Si dual-junction solar cells

Dual-junction solar cells formed by a GaAsP cell on a silicon bottom cell seem to be attractive candidates to materialize the long sought-for integration of III-V materials on Si for photovoltaic applications. In this study, we analyze several factors for the optimization of the bottom cell, namely, 1) the emitter formation as a result of phosphorus diffusion; 2) the growth of a high quality GaP nucleation layer; and 3) the process impact on the bottom subcell PV properties

Optimization of the secondary electron yield of laser-structured copper surfaces at room and cryogenic temperature

Electron cloud (e-cloud) mitigation is an essential requirement for proton circular accelerators in order to guarantee beam stability at a high intensity and limit the heat load on cryogenic sections. Laser-engineered surface structuring is considered a credible process to reduce the secondary electron yield (SEY) of the surfaces facing the beam, thus suppressing the e-cloud phenomenon within the high luminosity upgrade of the LHC collider at CERN (HL-LHC). In this study, the SEY of Cu samples with different oxidation states, obtained either through laser treatment in air or in different gas atmospheres or via thermal annealing, has been measured at room and cryogenic temperatures and correlated with the surface composition measured by x-ray photoelectron spectroscopy. It was observed that samples treated in nitrogen display the lowest and more stable SEY values, correlated with the lower surface oxidation. In addition, the surface oxide layer of air-treated samples charges upon electron exposure at a low temperature, leading to fluctuations in the SEY

Optimizing Bottom Subcells for III-V-on-Si MultiJunction Solar Cells

Dual-junction solar cells formed by a GaAsP or GaInP top cell and a silicon bottom cell seem to be attractive candidates to materialize the long sought-for integration of III-V materials on silicon for photovoltaic applications. Such integration would offer a cost breakthrough for photovoltaic technology, unifying the low cost of silicon and the efficiency potential of III-V multijunction solar cells. In this study, we analyze several factors influencing the performance of the bottom subcell of this dual-junction, namely, 1) the formation of the emitter as a result of the phosphorus diffusion that takes place during the prenucleation temperature ramp and during the growth of the III-V layers; 2) the degradation in surface morphology during diffusion; and 3) the quality needed for the passivation provided by the GaP layer on the emitter

A Framework for Simulating Home Control Networks

Non