1,720,980 research outputs found
From dye sensitized to perovskite solar cells: processes and materials for the forthcoming era of photovoltaic technology
No full textIn the context of the serious environmental issues, that Earth is facing, among which atmospheric CO2 increase is a crucial one, implementation of clean technologies is mandatory. The present PhD thesis concerns the study of two new third-generation PV technologies: Dye Sensitized Solar Cells (DSSCs) and Perovskite Solar Cells (PSCs). A typical DSSC is a low cost device of easy fabrication, widely investigated for indoor application, where the dye is used to collect light. In the former study, the research focused on natural dye extraction and the electrolyte optimization in the cell in accordance with a natural pigment. We realized and presented, for the first time in literature, a natural dye-based solar module of 8.7 cm2 with 1 % of power conversion efficiency (PCE), stable for 1000 hours. A PSC is a kind of solar cell that includes a perovskite-structured compound, most commonly a hybrid organic-inorganic lead halide-based material, as the light-harvesting active layer. Unlike DSSC, in PSC the liquid electrolyte has been replaced by a solid-state hole transport material (HTM), and since 2009 the run for boosting the PCE of PSC has started. In the latter study, the research focuses therefore on the optimization of an easy and low-cost PSC structure with a carbon layer replacing the HTM and gold usually used in a conventional high efficiency PSC. Despite all controversial studies on how moisture badly affects perovskite, it has been observed a beneficial water effect on the perovskite growth and formation in a 2-step deposition, which enhances the PCE of 12 % with respect to the non-treated cell
Comparison of Screen-Printing and Sputtered Isolation Layers in Graphite Based Perovskite Solar Cell and Efficiency Enhancement through Methylamine Induced Defect Healing
No full textExtraction and Characterization of Apocarotenoids (Cis-Norbixin and Cis-\ud Bixin) as Natural Sensitizers for Dye-Sensitized Solar Cells
No full textWe present a study on dye-sensitized solar cells (DSCs) based on apocarotenoids extracted from Achiote (Bixa orellana) a tropical shrub originating from the American continent. From the achiote seeds, we obtained a dark-red extract employing two new methods: one based on acetone and another based on diethyl ether. We studied the effect of the 4-tert-butyl-pyrydin on the sensitizer performances and the effect of the thickness of TiO2 layers. Bixin’s solar conversion efficiency was deeply improved by a progressive optimization of the photoanode TiO2 multilayer and of the electrolyte compositions overcoming the best performance reported in literature so far. It’s worth to emphasize that, although presently bixin based DSCs are still below the efficiency requirements for practical applications, our results indicate that these pigments are promising candidates to be potentially exploited, in the future, for production of non-toxic, cheap and fully biodegradable tandem dye-sensitized solar cells and as co-sensitizers since their absorption spectra is complementary to that of others dyes
Chlorophyll-c from marine algae and its characterization as natural dye for dye-sensitized solar cells.
No full textMarine algae (seaweeds) have a broad range of applications in several productive sectors, from human consumption to pharmacology, cosmetics, agriculture and waste water treatments. Algal biomass are also employed in the field of renewable energies for the production of biogas. Marine algae are indeed a reserve of natural dyes (Chls a, b and c), being therefore potentially suitable in PV technology for their low cost and easy attainability, without potential environmental load in terms of land subtraction. Chlorophyll-c is a photosynthetic pigment, a porfirine molecule, presents only in brown algae. Undaria pinnatifida (known as Wakame) is largely present in Venice Lagoon and for it a disposal strategy is recommended.
In this study, a low cost and eco-friendly extraction protocol was developed to obtain chlorophyll-c from brown alga Undaria pinnatifida, for utilization in dye-sensitized solar cells (DSSCs), along with the characterization of optical absorption and spectroscopy of the dye. Photovoltaic performances of the chlorophyll-based devices were also tested by measuring current-voltage curves as well as the incident photon to current efficiency. Three different solvents were tested, whose polarity was modified with different dilution with water. Better chlorophyll-c was extracted using 60% of acetone, whereas Ritchie algorithms were used to determine chlorophyll concentrations. The UV absorbance spectrum of chlorophyll extract exhibits the characteristic absorption peaks at 630 nm, confirming the presence of chl-c. The DSSC has delivered a short-circuit photocurrent density (Jsc) of 1.739 mA/cm2, open circuit photo-voltage (Voc) of 0.407 V, fill factor (FF) of 0.67, an efficiency (η) of 0.49% and a maximum incident photon-to-current conversion efficiency (IPCEmax) of 16% atthe Soret peak. The data presented here, improving η and IPCEmax , exceed the prior art of our previous study.[1] Obtained data suggest that protocols developed are useful to get an optimum amount of chlorophyll-c and that the DSSC performance indicates the possible use of marine algae in sustainable energy technologies.[1] G. Calogero, I. Citro, G. Di Marco, S. Armeli Minicante, M. Morabito and G. Genovese, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 117 (2014) 702
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
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