1,720,958 research outputs found
Lamination Processes in Organic Photovoltaics for Indoor Applications
No full textThe rise of the Internet of Things (IoT) has brought a growing need for reliable, sustainable ways to power connected devices. Currently, most of them rely on batteries, which come with challenges such as frequent replacement, maintenance, toxicity concerns, and recycling issues. Organic photovoltaics (OPVs) are a promising alternative thanks to their energy-efficient production, lower environmental impact, and design flexibility. One of the key strengths of OPVs lies in the ability to tailor the chemistry of organic semiconductors to fine-tune their optoelectronic properties for optimal performance. This makes them highly appealing for powering IoT sensors and devices, especially in indoor environments. Indoor OPVs work by converting ambient light into electricity through an active layer made of a blend of two organic semiconductors, placed between two electrodes. While newly developed polymer donor:non-fullerene acceptor (NFA) indoor OPVs have demonstrated impressive power conversion efficiencies (PCE) of up to 30% under warm LED lighting, a challenge remains: designing devices that are both efficient and compatible with upscaling. The transition from academic, laboratory-scale devices to scalable manufacturing processes is still limited, and the key criteria for successful rollto- roll (R2R) production have yet to be fully achieved to enable commercial impact in the IoT market. This thesis explores scalable device architectures using a lamination-based fabrication method developed at Epishine, where I carried out my PhD research. In this approach, the cathode and anode sides are processed separately using solution-based techniques and then laminated under heat and pressure to form a functioning indoor OPV. Unlike conventional lab-scale methods, this strategy allows for novel device architectures and provides flexibility to explore new materials. It also offers a valuable platform for investigating various failure modes that can emerge during the transition to scalable processing. Although NFAs have pushed the efficiency limits of OPVs, fullerene-based systems remain widely used in industrial contexts due to their stability, established processing, and reproducibility. While fullerenes are not typically used as electron transport layers (ETLs), the lamination process provides a unique opportunity to explore solution-processed fullerene interlayers at the active layer (AL)/cathode interface. In theory, such a structure should offer favorable energy alignment and efficient charge extraction; however, we observed unexpected voltage losses in laminated polymer:fullerene devices using a fullerene interlayer. Various solution-processable fullerene-based interlayers were therefore investigated, including blends with additives such as polyethyleneimine (PEI) or polystyrene (PS). When incorporated, these additives led to a reduction in the cathode work function, improving energy alignment and reducing voltage losses. Neutron reflectivity studies revealed that PEI tends to accumulate at the interface, which could block the movement of positive charges (holes). In contrast, PS creates a gradual layering effect through the film thickness, with its concentration changing from one side to the other. This smooth variation, called vertical gradient, may help reduce energy losses. These findings highlight how the structure and composition at the interface play a crucial role in improving charge extraction in indoor OPVs. One of the key issues investigated in this thesis was related to performance anomalies in laminated, thick, semi-transparent indoor OPVs. These devices exhibit unusual current density-voltage (J-V) characteristics, where performance is significantly better under cathode illumination compared to anode illumination. X-ray and neutron reflectivity measurements revealed vertical stratification in the active layer coated on the cathode side, a non-uniform distribution of materials through the film’s thickness, with the polymer component accumulating near the top surface. In contrast, the active layer deposited on the anode side was uniform. When the two layers were laminated together, the polymer-rich surface from the cathode side ended up in the center of the full active layer stack, resulting in a layered structure: active layer (anode side) / polymer-rich region / active layer (cathode side). Electrical simulations confirmed that this polymer-rich region was the primary cause of the J-V asymmetry. A model was proposed to describe this behavior, showing that electron extraction is hindered during anode illumination. Furthermore, laminated devices were developed with improved cathode/anode balance, achieving efficient and air-stable indoor OPV performance. A key priority in scaling up high-performing active-layer-based OPVs is transitioning to air processing with green solvents, while ensuring compatibility with upscaling requirements such as material cost, batch-to-batch variation, and suitability for R2R processing, all while maintaining high performance. We screened various wide-bandgap polymers and NFAs for indoor applications and developed a high-performing system that meets the requirements for large-scale printing. The PTQ10:FCC-Cl system demonstrates a PCE up to 25% under 500 lux, 4000K LED light. We also investigated why certain wide-gap system combinations failed during early screening. The results suggest that these systems struggle with charge generation, leading to lower PCE compared to the champion system.Funding agency: The Industrial PhD student program of the Swedish Foundation for Strategic Research (SSF)</p
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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