1,720,977 research outputs found
Electroplated nickel/tin solder pads for rear metallization of solar cells
No full textIn this study, we report on the feasibility of formation of nickel/tin solder pads and bus bars directly electroplated onto the aluminum screen-printed rear metallization layer of silicon-based solar cells. A localized wet processing technique via dynamic liquid drop/meniscus is used to perform the electrodeposition procedure. Excellent mechanical and electrical parameters of electroplated contacts are measured, thus proving the reliability of the proposed approach suitable for industrial application. Adhesion of electroplated nickel/tin solder pads is ensured through a two-step electrochemical pretreatment procedure, resulting in mean peel force values ranging from 2.5 to 3.8 N/mm. Electroplating of solder pads directly onto the screen-printed aluminum layer allows us to obtain a full homogeneous back surface field on the solar cell, resulting in an efficiency gain in 0.31-0.48%abs range. Furthermore, the proposed method completely removes the need for silver in the rear-side metallization layer of silicon-based solar cells
Low cost wax masking technique for electroplated metallization for solar cells application
No full textOptimal thermal annealing of a-SiOx layer obtained by pecvd for heterojunction solar cell application
No full textIn a-Si:H/c-Si heterojunction solar cells the UV absorption of amorphous layers limits the current generation. The use of a more transparent material like a-SiOx:H films is a key to further enhance the efficiency of this kind of cells. At the same time this layer must guarantee high surface passivation of the c-Si wafer to be suitable in high efficiency solar cell manufacturing. As for amorphous silicon, thermal annealing procedures are considered as valuable steps to enhance and stabilize thin film properties, when performed at opportune temperature. In order to avoid damages of the amorphous layer, each cell fabrication step should be carried at temperature lower than the emitter formation one. However, when thermal annealing is applied as one of the early fabrication step, the temperature can be high enough to obtain the best passivation properties. In this work we have analyzed the effect of several thermal treatments different for temperature, duration and surrounding atmosphere on a-SiOx:H/c-Si/a-SiOx:H structure. We have fully characterized the samples with the aid of effective lifetime evaluation and FTIR spectra to correlate the effect of thermal annealing to the a-SiOx:H/c-Si interface
Investigation of macroporous silicon as a material for ultra-thin photovoltaic cells
No full textIn this work we report the new type of ultra-thin photovoltaic cells that is possible to realize using freestanding macroporous silicon membranes. Study of macroporous silicon formation and membrane separation was carried out using p-type 1 and 10 Ohm·cm c-Si wafers and hydrofluoric acid containing electrolyte. Different passivation methods were used in order to investigate its effect on the lifetime of photo-generated carriers. The best lifetime response of 163 μs was measured for newly developed phosphorus light-diffusion passivation process. Relatively high lifetime value obtained indicates that a proper surface passivation may permit the fabrication of thin film photovoltaic cells using freestanding macroporous silicon membranes
Comparison between a-SiOx:H and a-Si:H as Passivation Buffer Layer for Heterojunction Solar Cells
No full textIn crystalline silicon based heterojunction solar cells the surface passivation quality is fundamental to obtain high efficiency. Intrinsic a-Si:H, as obtained by PECVD process from silane dissociation, is a good candidate for surface passivation, but UV absorption of this material limits the current generation. Moreover, surface passivation quality can be compromised when fabrication steps, following the a-Si:H deposition, exceed the a-Si:H deposition temperature. Both drawbacks can be overcome introducing a source of oxygen in PECVD process, obtaining a-SiOx:H layer that provides at the same time high quality passivation, wider optical bandgap and less susceptible to temperature steps than a-Si:H.
In this work we compared two heterojunction solar cells different only for front side passivation layer, consisting of a-Si:H or a-SiOx:H. We monitored lifetime and implied Voc during fabrication steps and evaluated the final I-V characteristics and quantum efficiency. We found that the UV light soaking together with heating during subsequent sputtering process, increased lifetime of cell with a-SiOx:H more than that with a-Si:H. Likewise the cell having a-SiOx:H as passivation layer showed electrical parameters higher than the a-Si:H counterpart. Indeed Jsc and Voc were 1mA/cm2 and 20mV respectively higher in cell with a-SiOx:H than in cell with a-Si:H. In particular cell with a-SiOx:H layer achieved an encouraging implied Voc of 751mV
Metastability of a-SiOx:H thin films for c-Si surface passivation
No full textThe adoption of a-SiOx:H films obtained by PECVD in heterojunction solar cells is a key to further increase efficiency, because of its transparency in the UV with respect to the commonly used a-Si:H. On the other hand the application of amorphous materials like a-Si:H and SiNx on the cell frontside expose them to the mostly energetic part of the sun spectrum, leading to a metastability of their passivation properties. In this work we explore the reliability of a-SiOx:H thin film layers surface passivation on c-Si substrates under UV exposition, in combination with thermal annealing steps. Both p-and n-type doped c-Si substrates have been considered. To understand the effect of UV light soaking we monitored the minority carriers lifetime and Si-H and Si-O bonding, by FTIR spectra, after different exposure times to light coming from a deuterium lamp, filtered to UV-A region, and focused on the sample to obtain a power density of 500 uW/cm2. We found a certain lifetime decrease after UV light soaking in both p- and n-type c-Si passivated wafers. The role of a thermal annealing, which usually enhances the as-deposited SiOx passivation properties, is furthermore considered. In particular we monitored the UV light soaking effect on c-Si wafers after SiOx coating by PECVD and after a thermal annealing treatment at 250°C for 15'. We found that after UV exposure thermal annealing steps can be used as a tool for the c-Si passivation recovery
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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