1,721,023 research outputs found
Elucidating Charge Generation in Green-Solvent Processed Organic Solar Cells
Full text linkOrganic solar cells have the potential to become the cheapest form of electricity. Rapid increase in the power conversion efficiency of organic solar cells (OSCs) has been achieved with the development of non-fullerene small-molecule acceptors. Next generation photovoltaics based upon environmentally benign “green solvent” processing of organic semiconductors promise a step-change in the adaptability and versatility of solar technologies and promote sustainable development. However, high-performing OSCs are still processed by halogenated (non-environmentally friendly) solvents, so hindering their large-scale manufacture. In this perspective, we discuss the recent progress in developing highly efficient OSCs processed from eco-compatible solvents, and highlight research challenges that should be addressed for the future development of high power conversion efficiencies devices
Interface passivation for improving performance and stability in organic solar cells
Full text linkOver the past 30 years, the power conversion efficiency (PCE) of Organic solar cells (OSCs) has significantly improved from 1% to over 19%, positioning them as one of the promising technologies for addressing the 21st-century energy crisis. This dissertation investigates three approaches to improving the efficiency and stability of OSCs. The first part explores the blending of inorganic and organic materials to leverage their respective advantages and passivity their drawbacks, resulting in enhanced device efficiency. However, due to the intrinsic instability of the PM6:Y6 system. A widely used sunscreen material was introduced between the electron transport layer (ETL) and the active layer to block UV radiation from damaging the active layer, thereby improving device stability. This sunscreen material not only enhanced exciton extraction efficiency, increasing PCE, but also provided significant UV stability under high UV content simulated sunlight. ZnO, a popular ETL material in inverted solar cells, is not without its limitations. Post-deposition, the surface of ZnO often exhibits residual -OH groups, which have been shown to generate radicals under illumination, attacking the end groups of acceptor materials. To address this, the study introduced a self-assembled monolayer (SAM) on the ZnO surface to passivate these effects. This modification significantly improved both the efficiency and stability of the OSCs. Moreover, since these organic acids can function as both hole and electron transport layers, their application on both sides of the active layer further enhanced the device lifetime without substantial loss in PCE. In summary, this thesis demonstrates three straightforward and effective strategies for modifying charge transport materials in OSCs, addressing various challenges and enhancing both efficiency and stability. These approaches have the potential to contribute significantly to the future application of high-efficiency, stable solar cell devices
Charge photogeneration in organic donor/acceptor blends
Full text linkPolymer-small molecule blend films are of increasing interest in the field of organic solar
cells. This thesis employs transient absorption spectroscopy as a mean to study charge
photogeneration in these blend films. These studies allow identifying and addressing the
charge photogeneration efficiency-limiting processes in polymer:perylene diimide organic
solar cells.
We approach the question by considering the influence of nanomorphology and phase
segregation on charge photogeneration and recombination dynamics. We further report on
yield of charge separated species in polythiophene / perylene diimide blend films as a
function of electron acceptor’s energy levels. We find that, compared to polythiophene /
PCBM blend films, charge photogeneration is significantly enhanced. Correlations between
free energy for charge dissociation and charge photogeneration yield within different
polymer:acceptor series are observed and indicate the generality of this relationship.
Furthermore, the energetic model proposed to account for these results is consistent with the
well-established Onsager and Marcus theories. It can therefore be concluded that the yield of
photogenerated charges in polymer/acceptor systems is likely to be dependent upon the
excess vibrational energy of the bound radical pair, such that the key kinetic competition in
the photogeneration process is between vibrational relaxation and dissociation of this species
Simultaneously, we investigate photoinduced charge separation in solid films of two perylene
diimides and a donor-bridge-acceptor (D-B-A)molecule, exTTF-pcp-C60 relative to solution.
First we find Intramolecular charge separation and recombination is correlated with a
reduction in the yield of long-lived, intermolecular charge-separated species in the perylene
diimide dyad. In the D-B-A system we observe the exTTF-pcp-C60 motif in this case leads to
more charges than the reference compounds or a mixture of them but that the excited state of
the electron acceptor, the fullerene, suffers from concentration self-quenching which severely
affect the charge yield in solid films
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
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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