1,721,146 research outputs found
Sb2Se3 thin-film solar cells via low-temperature thermal evaporation technique.
Full text linkThere has been a lot of anomalies in the climate in recent years. The situation is getting worse with every passing day, this alarming situation is the talk of the town amongst the world’s scientific community. There has been a consistent search for cleaner and sustainable source of energy which can replace the conventional fossil fuel. To this date renewable energy such as solar, wind, ocean, hydrothermal are in application. Among these, solar photovoltaic (PV) is the most effective and widely used one due to its abundant availability and zero contribution to pollution. In order to harness this energy conventional wafer based solar cells were used which have high cost of production and a longer by back time. Second generation thin film based solar cells are the talk of the time as they can be produced with less consumption of material and energy and hence are economical. Three materials are currently in the market; they are amorphous silicon (a-Si), cadmium telluride (CdTe) and copper indium gallium selenide (CIGS). Amongst them, CIGS has shown the highest efficiency of above 20% in laboratory scale, while CdTe has the highest market share. A drawback with CIGS and CdTe technologies is the use of scarce and expensive elements indium and tellurium. It is therefore clear that these are issues which are of concern for long-term availability of CdTe and CIGS. It is in this context; investigations have been initiated all over the world for an alternative, abundant and non-toxic absorber material. Antimony chalcogenide (Sb2Se3, Sb2S, Sb2(S,Se)3) are promising absorber materials for thin film photovoltaic cells due to their high absorption coefficient (>104cm-1) and optimum direct band gap (~1.2eV). Sb2Se3 has excellent optoelectronic properties with low processing temperature these are key factors responsible for the growing interest within the PV community. The best performing cells have reached above 10% till date. This thesis entitled “Sb2Se3 thin film solar via low thermal evaporation technique” is a detailed study of the fabrication of Sb2Se3 absorber films by low temperature thermal evaporation technique. Films have been as deposited, vacuum annealed as well selenized and studied in detail in this thesis. The studies included in the thesis are divided into eight chapters
Towards Interactive Question Answering: An Ontology-Based Approach
No full textThe ability to provide both rich and natural answers with respect to a given question, and clear explanations for failures, is a crucial aspect for a future generation of Question Answering systems able to interact with a user. We argue that such abilities are necessarily based on a deep analysis of the content of both the question and the answer, and propose an ontology-based approach to represent the structure of a question-answer pair in the context of utterance. The approach is domain and language-independent and can be considered a general framework for both Open Domain Question Answering and Natural Language Interfaces to Databases. We provide definitions for an Interactive Question Answer (IQA) ontology which capture significant aspects of interaction, and suggest how dialogue templates based on the IQA ontology can model natural and rich dialogues with a user
Raman Spectroscopy and In Situ XRD Probing of the Thermal Decomposition of Sb2Se3 Thin Films
No full textA simple method for Ge incorporation to enhance performance of low temperature and non-vacuum based CZTSSe solar cells
No full textDespite the slow efficiency development, Cu2ZnSn(S,Se)4 still is a promising absorber material for solar cells for its easy and low cost way of fabrication and the abundance of its elements. Similarly, also CdTe faced a long period when the record efficiency would not improve over 16.5% until a different paradigm was introduced. CZTSSe, compared to other absorbers, has the advantage that can be successfully made by solution-based growth techniques which are unique for their low cost. However this is meaningful only if selenization process is not done at high temperatures and without complicated processes. So we have optimized an easy, low cost, non-vacuum fabrication process for Cu2(Zn,Sn)(S,Se)4 thin-film absorber layers by spin coating of precursor and subsequent lower temperature selenization. A precursor solution is deposited on a Mo coated glass and the stack is then annealed below 450 °C in Se atmosphere and without the application of toxic hydrazine. With this process, we have already presented efficiencies of around 5.5%, but in this work, we introduce a simple impurity inclusion process by treating the surface of the precursor film with chlorine-based compound containing either Na, K or Ge. This allows to improve the open circuit voltage and the current density, with an increase in efficiency of 25% compared to the non-treated sample. The structural modifications are addressed by X-ray diffraction, Raman spectroscopy, atomic force microscopy and scanning electron microscopy. Current-voltage, capacitance-voltage and drive level capacitance profiling are used to analyse performance and defect density in the finished devices
Effects of post-deposition annealing and copper inclusion in superstrate Sb2Se3 based solar cells by thermal evaporation
No full textEarth-abundancy, nontoxic constituent, along with excellent stability and optoelectronic properties make antimony selenide (Sb2Se3) one of the potential candidate for low cost photovoltaics. In this work, antimony selenide (Sb2Se3) thin films were prepared by low temperature thermal evaporation method and characterized. Solar cells were fabricated in the superstrate configuration of Glass/ITO/ZnO/CdS/Sb2Se3/Au. It was found that annealing in vacuum after Sb2Se3 deposition played a significant role in the device performance. One-dimensional crystal structure of Sb2Se3 with a preferred grain orientation was found to be beneficial for the higher performance of the solar cells with vacuum annealing at 300 degrees C. Furthermore, Cu addition after the deposition of Sb2Se3 was introduced to improve the back contact and the device performance. In particular, Cu addition as a back contact leads to a significant increase in the V-oc and the fill factor (FF). Moreover, aging of the finished cells during accelerated stability tests revealed a light soaking effect without degradation even in case of copper insertion. Our best solar cell showed a conversion efficiency of 3.5% without selenization
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
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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