1,721,015 research outputs found
How the amount of copper influences the formation and stability of defects in CdTe solar cells
Get PDFWith a 22.1% efficiency record and the successful results in terms of production yield, CdTe based thin film solar cells are today a competing technology with traditional silicon solar cells. Despite different copper-free back contacts have been applied, Cu is present in all the most performing CdTe devices. On the other hand, it is well known that Cu is a fast diffuser in CdTe, and it heavily influences the devices degradation; thus controlling its concentration is very important. In this paper a study of the influence of copper quantity on the performance of the devices and stability at the back contact is presented. CdTe cells fabricated with a 0.1 nm thick Cu layer are compared to devices fabricated with 2.0, 1.0 and 0.5 nm thick Cu layers. The amount of copper affects the performance and aging of the samples. Moreover an inversion of the bias dependency (solar cells in open circuit or in short circuit under current flow), during the aging, occurs in samples containing a copper layer below a certain thickness, suggesting that another degradation mechanism predominates
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Optimisation of CdTe(1-X)SeX and MgXZn(1-X)O layers for CdTe PV devices
Get PDFThis thesis presents a study on the optimisation of CdTe(1-X)SeX and MZO layers for CdTe PV applications. The first part of this work focused on the formation of the CdTe(1-X)SeX layers using CdSe layer and its impact on solar cell performance. Initially the incorporation of CdSe layer into conventional CdS/CdTe devices was investigated. This approach was found to be detrimental to all device parameters particularly JSC due to the formation of a CdS(1-X)SeX phase at the CdTe/CdSe/CdS interface. This phase increased the amount of parasitic absorption observed at short wavelength, reduced PV performance, and resulted in excessive void formation at the CdTe device interface. Replacement of CdS with SnO2 as the junction partner layer was found to increase the device photo response at both short and long wavelength due to removal of the CdS and efficient formation of the CdTe(1-X)SeX phase. This resulted in increased device performance of > 13% with notably high JSC values of > 29 mA cm-2. However, removal of CdS did result in a reduced VOC and interface voids were still present. Focus was then placed on alternative oxides to SnO2 which could act as the device window layer but simple binary oxides tested, ZnO, TiO2 and FTO were all found to reduce performance compared to SnO2. The second part of this work therefore investigated MZO layers for CdTe PV. Two approaches were studied, co-sputtering from ZnO and MgO targets or sputtering from a single MZO target. The use of co-sputtered MZO layers was found to be detrimental to performance, due to the high resistivity of the layers and the formation of S-shaped JV curves related to interface charge accumulation. Initially use of single target MZO layers similarly resulted in S-shaped curves and poor performance however, post-growth annealing of the MZO converted the material from amorphous to crystalline and enhanced conductivity of the MZO, removing the charge accumulation. Despite the reduced overall performance compared to SnO2, 11.3% and 13.5% respectively, the MZO devices had an improved VOC demonstrating that with further optimisation of the device junction interface further improvements to performance could be achieved
Impacts of Se Alloying and Diffusion on Optimal Fabrication Procedures for CdSe(x)Te(1−x) Solar Cells
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