1,721,020 research outputs found
Polycrystalline CdTe thin films solar cells
No full textABSTRACT: we report the state of the art of the second generation of solar cells, based on CdTe thin film technology. This type of cells reached on laboratory scale, photovoltaic energy conversion efficiencies of about 16.5% higher than those obtained with the bulk materials. In particular, we describe the materials, the layers sequence, the characteristic deposition techniques and the devices that are realized by adopting this semiconductor as absorber material. Particular emphasis will be placed on major innovations that have made possible to achieve high efficiencies with polycrystalline materials by showing how the thin-film technology is mature enough to be easily transferred to industrial production. We will focus our attention on a technological project, completely developed in Italy, with the aim to transfer the CdTe/CdS polycrystalline thin film photovoltaic module process to an industrial production
CdTe Solar Cells by Low Temperature Processes
No full textCdTe polycrystalline thin film solar cells have a strong potential in scalability. They have shown long-term stable performance and high efficiency up to 16.5% under AM1.5 illumination. Amongst several attractive features, high chemical stability of CdTe and a simple compound formation are the most important ones for large area production of solar modules. A further simplification has been done by substituting the CdCl2 step by treating CdTe films in an atmosphere containing a non toxic gas that is inert at room temperature, like HCF2Cl, that belongs to the Freon© family. The treatment temperature is typically 400°C, for a few minutes and in an atmosphere containing Cl, typically 100 mbar of Ar containing 15% of HCF2Cl. The change in the morphology of CdTe films after treatment is very similar to that obtained with CdCl2 treatment and an increase in the size of small grains is always observed. This process has been applied by N. Romeo et al. on CdTe deposited by close-spaced sublimation (CSS) with very interesting results (15.8% efficiency). The application of the regular CdCl2 treatment and of this novel “activation process” on low and high temperature processed solar cells will be described Moreover, there are new promising device configurations like bifacial solar cells, ultra-thin solar cells and flexible devices. The highest efficiencies in CdTe solar cells have been obtained using CSS deposition method, which requires a high substrate temperature (500÷550 °C). Instead, conventional physical vapor deposition (PVD) process where CdTe is evaporated in a high vacuum evaporation (HVE) system at lower substrate temperatures (typically 300°C) has provided solar cells with efficiencies of more than 12%. For these reasons HVE process is attractive for a very simple in-line deposition of large area CdTe solar modules on soda-lime glass substrates, as well as on polymer foils thereby facilitating the roll-to-roll manufacturing of flexible solar modules
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
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
Introduction to Inorganic Thin Film Solar Cells
No full textSolar energy represents the largest energy input into the terrestrial system. Although photovoltaics is not the sole answer to the myriad of energy challenges offered by the clean and economical use of sun spectrum, this renewable energy option can make an important contribution to the economy of each country. Despite its relatively low power density, the solar electricity market is booming. By the end of 2007, the cumulative installed capacity of solar photovoltaic (PV) systems around the world had reached more than 9,200 MW. This compares with a figure of 1,200 MW at the end of 2000. Installations of PV cells and modules around the world have been growing at an average annual rate of more than 35% since 1998. The EPIA/Greenpeace Advanced Scenario [1] shows that by the year 2030, PV systems could be generating approximately 2,600 TWh of electricity around the world to satisfy the electricity needs of almost 14% of the world’s population Photovoltaics stumbling block has always been its cost but it has held the promise of providing clean electricity and competitive rates. The cost is declined by a factor of nearly 150-160 times since the invention in 1954 of the modern solar cell based on crystalline silicon technology. More then 90% of the current production uses 1st generation PV wafer based cSi (1st G PV) a technology with the ability to continue to reduce its cost at its historic rate. The direct production costs for crystalline silicon modules are expected to be around 1 €/Wp in 2013, below 0.75 €/Wp in 2020 and lower in the long term as indicated in table 1 [5]
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
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