1,721,025 research outputs found
Nanopatterning for light trapping in thin film crystalline silicon solar cells
Full text linkLAUREA MAGISTRALEL'aumento progressivo della domanda di moduli fotovoltaici in silicio mono-cristallino, oggi tecnologia di punta nel campo dell'industria per la produzione di energia elettrica, ha posto la ricerca di fronte a importanti sfide in relazione al bisogno di sviluppare tecnologie che garantiscano da un lato costi sostenibili e dall'altro ottime prestazioni.
Per ragioni legate al costo del materiale attivo, è stato intrapreso lo sviluppo della tecnologia a film sottile. Ciononostante, nel momento in cui si considerano spessori minimi per il materiale attivo, vengono riscontrati parecchi inconvenienti riguardanti le perdite ottiche e sembra che i metodi convenzionali di intrappolamento della luce non siano compatibili a causa del consumo eccessivo del materiale.
Il progetto in questione intende investigare un modello della superficie del film sottile su silicio su scala di dimensioni inferiori alle lunghezze d'onda del visibile, al fine di ridurre la riflettanza all'interfaccia e aumentare l'efficienza di cattura della luce nel substrato con relativo basso consumo del materiale. Questa idea di modello sarà presentata per mezzo di due differenti tecnologie: hole-mask colloidal lithography e nano-imprint lithography.
Hole-mask colloidal lithography è una tecnica litografica che consiste nella dispersione casuale di particelle colloidali in soluzione sulla superficie del silicio, la deposizione di un film sottile di una maschera di allumino, rimozione delle particelle colloidali e la rimozione di materiale attivo attraverso le forature sulla maschera mediante il reactive ion etching.
Nano-imprint lithography, consiste nel trasferimento di un reticolo di diffrazione da uno stampo prefabbricato sulla superficie del silicio attraverso una deformazione meccanica: la superficie del silicio viene inizialmente coperta con un resist termoplastico, lo stampo viene quindi pressato sul silicio attraverso uno strumento meccanico ed infine il silicio viene rimosso mediante il reactive ion etching.The increasing demand of crystalline silicon based Photovoltaics as a leading technology in the electrical power generation industry has brought research to face several challenges related to the need to go to cost effective technologies that still do not neglect the performances. Because of the costs related to the active material, thin _lm technology has been proposed. Nevertheless, several issues related to optical losses arise when considering low thicknesses for the active material and conventional light trapping methods seems to be not compatible due to the total material consumption. In this work, the idea of a sub wavelength-scale patterning on thin _lm silicon surface, in order to reduce front side reflectance and increase light trapping inside the bulk with low material consumption, will be presented by means of two different technologies: hole-mask colloidal lithography and nano-imprint lithography.
Hole-mask colloidal lithography is a technique that utilizes random dispersion of colloidal particles, on silicon surface, to define the pattern. This work will be focused on the absorption enhancement provided by such technology.
Nano-imprint lithography consists of transferring a pattern from a prefabricated stamp to the silicon surface by means of a mechanical press. In this work optical result will be presented, together with cell results. The deteriorating effect on carrier lifetime will be analyzed and different solution to that issue will be proposed
Disordered nanostructures by hole-mask colloidal lithography for advanced light trapping in silicon solar cells
Full text linkWe report on the fabrication of disordered nanostructures by combining colloidal lithography and silicon etching. We show good control of the short-range ordered colloidal pattern for a wide range of bead sizes from 170 to 850 nm. The inter-particle spacing follows a Gaussian distribution with the average distance between two neighboring beads (center to center) being approximately twice their diameter, thus enabling the nanopatterning with dimensions relevant to the light wavelength scale. The disordered nanostructures result in a lower integrated reflectance (8.1%) than state-of-the-art random pyramid texturing (11.7%) when fabricated on 700 mu m thick wafers. When integrated in a 1.1 mu m thin crystalline silicon slab, the absorption is enhanced from 24.0% up to 64.3%. The broadening of resonant modes present for the disordered nanopattern offers a more broadband light confinement compared to a periodic nanopattern. Owing to its simplicity, versatility and the degrees of freedom it offers, this potentially low-cost bottom-up nanopatterning process opens perspectives towards the integration of advanced light-trapping schemes in thin solar cells
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Passivation of photonic nanostructures for crystalline silicon solar cells
No full textWe report on the optical and electrical performances of periodic photonic nanostructures, prepared by nanoimprint lithography (NIL) and two different etching routes, plasma, and wet chemical etching. Optically, these periodic nanostructures offer a lower integrated reflectance compared with the industrial state-of-the-art random pyramid texturing. However, electrically, they are known to be more challenging for solar cell integration. We propose the use of wet chemical etching for fabricating inverted nanopyramids as a way to minimize the surface recombination velocities and maintain a conventional cell integration flow. In contrast to the broadly used plasma etching for nanopatterning, the wet chemically etched nanopatterning results in low surface recombination velocities, comparable with the state-of-the-art random pyramid texturing. Applied to 40-mu m thick epitaxially grown crystalline silicon foils bonded to a glass carrier superstrate, the periodic-inverted nanopyramids show carrier lifetimes comparable with the non-textured reference foils ((eff)=250 mu s). We estimate a maximum effective surface recombination velocity of similar to 8cm/s at the patterned surface, which is comparable with the state-of-the-art values for crystalline silicon solar cells. Copyright (c) 2014 John Wiley & Sons, Ltd.EC [309127
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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