1,721,070 research outputs found
Chlorophylls and xanthophylls of crop plants as dyes for Dye-Sensitized Solar Cells (DSSC)
Full text linkNatural dyes have become a viable alternative to expensive and rare organic sensitizers because of their low cost, easy attainability, abundance of supply of raw materials and environmental friendliness. Chlorophyll, the most abundant pigment, can be extracted from plant leaves with simple and inexpensive methods, but it’s diffi cult to use as a Dye-Sensitized Solar Cells (DSSC) sensitizer due to the absence of OH and COOH groups. The opposite is true for xanthophylls, a particular class of carotenoids that contain free hydroxyl groups and thus may be considered as potential DSSC sensitizers. In this work we describe a new and inexpensive method of chlorophyll extraction from leaves based on the use of a basic solvent that provides the creation of COOH groups, allowing chlorophyll binding on the TiO2 layer. This modifi ed chlorophyll dye showed a higher DSSC effi ciency level (0.72%) compared to xanthophylls, which had lower efficiency
Beyond 99.5% geometrical fill factor in perovskite solar minimodules with advanced laser structuring
No full textPerovskite solar cells, known for high efficiency and compatibility with various photovoltaic (PV) applications, have garnered significant attention from academia and industry. Scaling up these cells conventionally involves fabricating modules with series-connected cells using a monolithic interconnection based on the P1-P2-P3 scheme, a common approach for thin-film PV modules. The Geometrical Fill Factor (GFF), representing the ratio between active area and aperture area, typically ranges from 90% to 95%. This study introduces an advanced laser manufacturing process to minimize interconnection area by reducing scribe width and minimizing distances between them, achieving an interconnection width of 45 mu m with a GFF of 99.1%. Additionally, a discontinuous P2 design further reduces the dead area to an average of 19.5 mu m, resulting in a record GFF of 99.6%. Using this interconnection in a highly efficient p-i-n stack, the study demonstrates the feasibility of the discontinuous P2 by fabricating 2.6 cm2 minimodules with an aperture area efficiency of 20.7%. The research highlights how proper design can minimize intrinsic losses during the scaling process from cell to module to a negligible level. Experimental studies, coupled with cell-to-module loss simulations and electroluminescence mapping for layer deposition uniformity, provide insights into the potential of the new P2 design.A novel discontinuous interconnection based on a dashed P2 contact is developed to minimize the efficiency losses from cell to module. In this way, it is possible to achieve a record geometrical fill factor of 99.6% (active area divided by the sum of active area and interconnection area), without inducing any resistive losses, achieving a minimodule efficiency of 20.6%
Anodically electrodeposited NiO nanoflakes as hole selective contact in efficient air processed p-i-n perovskite solar cells
No full textNanostructured NiO as hole selective contact for perovskite solar cells is deposited on ITO from the potentiostatic anodic electrodeposition of NiOOH. Along with the large surface extension due to the honeycomb-like morphology, the electrodeposition route imparts different electrochemical features in respect to the classic sol-gel!derived NiO, which are two interesting features for optoelectronic applications. CH3NH3PbI3 is deposited in ambient atmosphere on the NiO substrates to fabricate p-i-n perovskite solar cells, with PCBM and solution processed BCP as electron selective contact and silver as counter electrode. We found that the performances are strongly dependent on the deposition potential, with the PCE increasing when going from 1.00 V to 1.10 V vs Ag/AgCl. The best efficiency obtained is 16.1%, thanks to a fill-factor of 78%. Notably, the electrodeposited layer outperformed the sol-gel spin-coated one, proving the effectiveness of electrosynthesis to achieve competitive selective contacts for perovskite photovoltaics
Investigating the electrodeposition mechanism of anodically grown NiOOH films on transparent conductive oxides
No full textElectrodeposition of NiOOH is an attracting route toward nanosized films of NiO, a p-type semiconductor used in many advanced applications. In this paper, the deposition mechanism is thoroughly investigated aiming at the clarification of the deposition dynamics and the chemical nature of the deposit. We focused on initial stages of the potentiostatic deposition on ITO, which yields a nanostructured film. In the potential range investigated the process is mass transport controlled and strongly overlaps with oxygen evolution reaction. The nucleation regime, which is finely tunable, correlates with the surface extension of the film. Supporting electrolytes are found to suppress the deposition, likely by modifying the nickel speciation in the aqueous electrolyte. Further, through XPS investigation we shed light on the mixed γ−β NiOOH nature of the deposited film and its electrochemistry. This work provides precious understanding for future exploitations of anodic electrodeposited NiO, especially in applications where a strict control on surface morphology and thickness at the nanoscale level is mandatory
The effect of water in Carbon-Perovskite Solar Cells with optimized alumina spacer
No full textPerovskite solar cells with carbon back contact (C-PSC) represent a promising architecture that allows for a simplification of the manufacture process and a stabilization of the cell performances. In this work, we designed a fully printable C-PSC using a homemade mesoporous alumina (Al2O3) ink. By increasing the alumina layer thickness we show that fill factor reduces, short-circuit current increases, while open circuit voltage increases until a thickness of 1.2 mu m. In order to improve performances of PSCs, we investigated a water pre-treatment before perovskite deposition. We show that water pre-treatment improves pore filling, leads to a reduction of charge recombination, and improves the conversion of PbI2 crystals into perovskite. The water pre-treatment permits to obtain an average efficiency increasing of 16% with respect to cells without water pre-treatment
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
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