1,721,107 research outputs found
Nanosecond long excited state lifetimes observed in hafnium nitride
No full textAbstract Not AvailableSimon Chung, Xiaoming Wen, Shujuan Huang, Neeti Gupta, Gavin Conibeer, Santosh Shrestha, Takaaki Harada, Tak W. Ke
Optical Performance of Ag-based Back Reflectors with different Spacers in Thin Film Si Solar Cells
Get PDFAbstractWe have compared different Ag-based back reflectors (BRs) applied to superstrate-type microcrystalline Si devices grown on Asahi U glass. In particular, substitution of the conventional ZnO:Al layer by MgF2, with lower refractive index and no free-carrier absorption, has been investigated. As electrical issues can mask the optical performance of the BR when evaluated by EQE measurements, a purely optical method that compares the intensity of Raman spectra generated with long wavelength excitation light has been applied. Based on this investigation, MgF2/Ag is potentially superior to ZnO:Al/Ag, even when MgF2 is used in the form of ultrathin layer (few nm, likely island-like). Nevertheless, the novel dual-function n-SiOx/Ag BR outperforms all the other BRs
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
Active layer limitations and non-geminate recombination in polymer-fullerene bulk heterojunction solar cells
No full textThis chapter has focused on the apparent thickness limitations of most high performance donor-acceptor bulk heterojunction solar cells, which pose significant challenges to achieving 15% conversion efficiency. Efficiencies approaching this value require high external quantum efficiencies and high fill factors using thick photoactive layers. An extensive literature review showed that only a handful of high performance donor-acceptor bulk heterojunction solar cells maintain high fill factor at film thicknesses larger than 200 nm, with PBnDT-FTAZ, DT-PDPP2T-TT, PtPD3T and PDTSiTTz being notable exceptions. Apart from difficulties in controlling active layer morphologies with increasing layer thickness and space charge layer formation in (often inadvertently) doped bulk heterojunctions, Langevin-type bimolecular recombination is shown to limit charge extraction efficiency in thick devices, thereby leading to low fill factors. Using time-resolved charge extraction techniques such as photo-CELIV, TOF and time-resolved charge extraction, reduced (non-Langevin) bimolecular recombination is demonstrated for PDTSiTTz:PCBM heterojunctions. A brief review of 12 models offering possible explanations for such reduced recombination is presented. This highlights the fact that developing a onesize- fits-all, unified model of reduced recombination is challenging due to the limited number of reduced recombination donor-acceptor systems and the differences in experimental techniques and sample preparation between various reports. Resolving this rather intriguing, fundamentally important issue by establishing design rules for advanced donor-acceptor bulk heterojunction solar cells will be an important milestone affecting not only the performance of laboratory-based devices, but also the commercialization of this low-cost photovoltaic technology
- …
