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1
Will ultrathin CIGS solar cells overtake the champion thin-film cells? Updated SCAPS baseline models reveal main differences between ultrathin and standard CIGS
Publicaçãopor Violas, André F.Outros Autores: Oliveira, António J.N.; Teixeira, Jennifer P.; Lopes, Tomás S.; Barbosa, João R.S.; Fernandes, Paulo A. et al.Cu(In,Ga)Se2 (CIGS) solar cells are amongst the best performing thin-film technologies, with the latest performance gains being mainly due to recent years improvements obtained with post-deposition treatments (PDT). Moreover, thinning of the absorber layer down to sub-micrometre values (ultrathin absorbers) is of extreme importance for CIGS to be even more cost-effective and sustainable. However, electrical and optical limitations, such as rear interface recombination and insufficient light absorption, prevent the widespread implementation of ultrathin CIGS devices. The recent electrical CIGS simulation baseline models have failed to keep up with the experimental developments. Here an updated and experimentally based baseline model for electrical simulations in the Solar Cell Capacitor Simulator (SCAPS) software is presented and discussed with the incorporation of the PDT effects and increased optical accuracy with the support from Finite-Difference Time-Domain (FDTD) simulation results. Furthermore, a champion solar cell with an equivalent architecture validates the developed thin-film model. The baseline model is also applied to ultrathin CIGS solar cell devices, validated with the ultrathin champion cell. Ultimately, these ultrathin models pave the way for an ultrathin baseline model. Simulations results reveal that addressing these absorbers' inherent limitations makes it possible to achieve an ultrathin solar cell with at least 21.0% power conversion efficiency, with open-circuit voltage values even higher than the recent thin-film champion cells. -
2
Evaluation of the Biological Potential of Himanthalia elongata (L.) S.F.Gray and Eisenia bicyclis (Kjellman) Setchell Subcritical Water Extracts
Publicaçãopor Gomes, InêsOutros Autores: Rodrigues, Helena; Rodrigues, Carla; Oliveira, Marta Marques; Paíga, Paula; Paiva, Alexandre et al.Neuroprotection is a need that remains unmet in treating chronic neurodegenerative disorders, despite decades of extensive research. To find new neuroprotective compounds, extracts of Himanthalia elongata (L.) S.F.Gray and of Eisenia bicyclis (Kjellman) Setchell were obtained through subcritical water extraction applying a four-step temperature gradient. The fractions obtained were screened against brain enzymes involved in neurodegenerative etiology, namely in Alzheimer’s and Parkinson’s diseases, and against reactive oxygen and nitrogen species, all contributing factors to the progression of neurodegeneration. Results showed no significant enzyme inhibition but strong radical scavenging activities, particularly in the fourth fraction, extracted at the highest temperature (250 °C), highlighting their ability to retard oxidative and nitrosative stresses. At higher temperatures, fractions were composed of phenolic compounds and Maillard reaction products, a combination that contributed to their antioxidant activity and, consequently, their neuroprotective properties. All fractions were evaluated for the presence of iodine, 14 organochlorine and 7 organophosphorus pesticides, and pharmaceuticals used in Alzheimer’s and Parkinson’s diseases (14), psychiatric drugs (8), and metabolites (8). The fractions studied did not present any of the screened contaminants, and only fraction 1 of E. bicyclis should be used with caution due to iodine content. -
3
Biodegradation of mono-, di- and trifluoroacetate by microbial cultures with different origins
Publicaçãopor Alexandrino, Diogo A.M.Outros Autores: Ribeiro, Inês; Pinto, Luís M.; Cambra, Rafael; Oliveira, Rui S.; Pereira, Filipe et al.This work focused on the biodegradation of three structurally related fluoroacetates (FAs), mono- (MFA), di- (DFA) and trifluoroacetate (TFA), using as microbial inocula samples collected from a site with a long history of industrial contamination and activated sludge obtained from a municipal wastewater treatment plant. Biodegradation experiments were carried out under different modes of substrate supplementation, which included (i) FAs fed as sole carbon sources; (ii) FAs (only for DFA and TFA) fed in co-metabolism with sodium acetate; and (iii) mixtures of MFA with DFA or TFA. Biodegradation of the target compounds was assessed through fluoride ion release. Defluorination was obtained in the cultures fed with MFA, while DFA and TFA were recalcitrant in all tested conditions. When present in mixture, DFA was shown to inhibit biodegradation of MFA, while TFA had no effect. A total of 13 bacterial isolates obtained from MFA degrading cultures were found to degrade 20mgL-1 of this compound, as single strains, when supplemented as a sole carbon source. Sequencing of the 16S rRNA gene indicated that among these degrading bacteria only Delftia acidovorans had been previously reported to be able to degrade MFA. This work shows that, despite their similar chemical structures, biodegradation of the three tested FAs is very distinct and draws attention to the unknown impacts that the accumulation of DFA and TFA may have in the environment as a result of their high recalcitrance. -
4
Cu(In,Ga)Se2 based ultrathin solar cells: the pathway from lab rigid to large scale flexible technology
Publicaçãopor Lopes, TomásOutros Autores: Teixeira, Jennifer; Curado, Marco; Ferreira, Bernado; Oliveira, Antonio; Cunha, José et al.For the first time, the incorporation of interface passivation structures in ultrathin Cu(In,Ga)Se2 (CIGS) based solar cells is shown in a flexible lightweight stainless-steel substrate. The fabrication was based on an industry scalable lithography technique - nanoimprint lithography (NIL) - for a 15x15 cm2 dielectric layer patterning, needed to reduce optoelectronic losses at the rear interface. The nanopatterning schemes are usually developed by lithographic techniques or by processes with limited scalability and reproducibility (nanoparticle lift-off, spin-coating, etc). However, in this work the dielectric layer is patterned using NIL, a low cost, large area, high resolution, and high throughput technique. To assess the NIL performance, devices with a NIL nanopatterned dielectric layer are benchmarked against electron-beam lithography (EBL) patterning, using rigid substrates. Up to now, EBL is considered the most reliable technique for patterning laboratory samples. The device patterned by NIL shows similar light to power conversion efficiency average values compared to the EBL patterned device - 12.6 % vs 12.3 %, respectively - highlighting the NIL potential for application in the solar cell sector. Moreover, the impact of the lithographic processes, such as different etch by-products, in the rigid solar cells’ figures of merit were evaluated from an elemental point of view via X-ray Photoelectron Spectroscopy and electrically through a Solar Cell Capacitance Simulator (SCAPS) fitting procedure. After an optimised NIL process, the device on stainless-steel achieved an average power conversion efficiency value of 11.7 % - a slightly lower value than the one obtained for the rigid approach, due to additional challenges raised by processing and handling steel substrates, even though scanning transmission electron microscopy did not show any clear evidence of impurity diffusion towards the absorber. Notwithstanding, time-resolved photoluminescence results strongly suggested the presence of additional non-radiative recombination mechanisms in the stainless-steel absorber, which were not detected in the rigid solar cells, and are compatible with elemental diffusion from the substrate. Nevertheless, bending tests on the stainless-steel device demonstrated the mechanical stability of the CIGS-based device up to 500 bending cycles. -
5
Exploiting the Optical Limits of Thin‐Film Solar Cells: A Review on Light Management Strategies in Cu(In,Ga)Se 2
Publicaçãopor Oliveira, António J. N.Outros Autores: Teixeira, Jennifer P.; Ramos, Duarte; Fernandes, P. A.; Salomé, Pedro M. P.Light management strategies are of utmost importance to allow Cu(In,Ga)Se2 (CIGS) technology market expansion, as it would enable a conversion efficiency boost as well as thinner absorber layers, increasing sustainability and reducing production costs. However, fabrication and architecture constraints hamper the direct transfer of light management architectures from other photovoltaic technologies. The demand for light management in thin and ultrathin CIGS cells is analyzed by a critical description of the optical loss mechanisms in these devices. Three main pathways to tackle the optical losses are identified: front light management architectures that assist for an omnidirectional low reflection; rear architectures that enable an enhanced optical path length; and unconventional spectral conversion strategies for full spectral harvesting. An outlook over the challenges and developments of light management architectures is performed, establishing a research roadmap for future works in light management for CIGS technology. Following the extensive review, it is expected that combining antireflection, light trapping, and conversion mechanisms, a 27% CIGS solar cell can be achieved. -
6
Use of Bioproducts Derived from Mixed Microbial Cultures Grown with Crude Glycerol to Protect Recycled Concrete Surfaces
Publicaçãopor Serrano-González, LorenaOutros Autores: Merino-Maldonado, Daniel; Guerra-Romero, Manuel Ignacio; Morán-Del Pozo, Julia María; Lemos, Paulo Costa; Pereira, Alice Santos et al.Origem: Repositório Institucional da UNLThe large increase in the world population has resulted in a very large amount of construction waste, as well as a large amount of waste glycerol from transesterification reactions of acyl glycerides from oils and fats, in particular from the production of biodiesel. Only a limited percentage of these two residues are recycled, which generates a large management problem worldwide. For that reason, in this study, we used crude glycerol as a carbon source to cultivate polyhydroxyalkanoates (PHA)-producing mixed microbial cultures (MMC). Two bioproducts derived from these cultures were applied on the surface of concrete with recycled aggregate to create a protective layer. To evaluate the effect of the treatments, tests of water absorption by capillarity and under low pressure with Karsten tubes were performed. Furthermore, SEM-EDS analysis showed the physical barrier caused by biotreatments that produced a reduction on capillarity water absorption of up to 20% and improved the impermeability of recycled concrete against the penetration of water under pressure up to 2.7 times relative to the reference. Therefore, this bioproduct shown to be a promising treatment to protect against penetration of water to concrete surfaces increasing its durability and useful life. -
7
Multi-step subcritical water extracts of fucus vesiculosus l. And codium tomentosum stackhouse
Publicaçãopor Soares, CristinaOutros Autores: Paíga, Paula; Marques, M. Manuel B.; Neto, Tânia; Carvalho, Ana Paula; Paiva, Alexandre et al.Origem: Repositório Institucional da UNLMental health and active aging are two of the main concerns in the 21st century. To search for new neuroprotective compounds, extracts of Codium tomentosum Stackhouse and Fucus vesiculosus L. were obtained through multi-step (four step) subcritical water extraction using a temperature gradient. The safety assessment of the extracts was performed by screening pharmaceutical compounds and pesticides by UHPLC-MS/MS, and iodine and arsenic levels by ICP-MS. Although the extracts were free of pharmaceutical compounds and pesticides, the presence of arsenic and high iodine contents were found in the first two extraction steps. Thus, the health-benefits were only evaluated for the fractions obtained in steps 3 and 4 from the extraction process. These fractions were tested against five brain enzymes implicated in Alzheimer’s, Parkinson’s, and major depression etiology as well as against reactive oxygen and nitrogen species, having been observed a strong enzyme inhibition and radical scavenging activities for the step 4 fractions from both seaweed species. Regarding the variation of the chemical composition during the extraction, step 1 fractions were the richest in phenolic compounds. With the increase in temperature, Maillard reaction, caramelization and thermo-oxidation occurred, and the resulting products positively affected the antioxidant capacity and the neuroprotective effects. -
8
Turn-taking in free-play interactions
Publicaçãopor Lourenço, VladimiroOutros Autores: Serra, Juliana; Coutinho, Joana; Pereira, Alfredo F.Origem: Repositório Institucional da UNLTurn-transition timing in childhood has been examined by measuring response latency – that aggregates gap and overlap duration – in turn-transitions contingent to specific semantic categories. This contrasts with studies in infancy where the whole spectrum of temporal contingent vocalizations are examined, and gap and overlap duration is analyzed independently. We propose using the latter approach to investigate the continuities between infancy and childhood. In a cross-sectional design, we analyzed the vocalizations of 44 mother-child free-play interactions, ranging from three to five years of age. Frequency and duration were measured for gaps and overlaps, independently, and as an aggregated measure – floor-transfer offset (FTO). The effects of child's age and direction of turn-transition (child, mother) were assessed using generalized linear mixed modeling for each dependent variable (DV: FTO, gaps, overlaps). Although there was a slight increase in FTO and gap duration across ages, no significant effect of age was found for any of the DVs. There was an effect of turn-transition direction, for FTO and gap durations, but not for overlap duration. Specifically, mother-to-child turn-transitions produced significantly longer FTO and gap durations than child-to-mother turn-transitions, but had similarly timed overlaps. Results suggest that gaps and overlaps still have different developmental trajectories throughout childhood, and that overlap duration converges to adult standards, at least, by 3-years of age. Methodologically, we demonstrated the relevance of using complementary metrics (FTO, gap, overlap) to understand the developmental trajectories of turn-taking, and that examining all temporally contingent vocalizations can provide a valid and more inclusive measure of turn-transition duration in childhood. -
9
Occurrence and seasonal variation of several endocrine disruptor compounds (pesticides, bisphenols, musks and UV-filters) in water and sediments from the estuaries of Tagus and Dou...
Publicaçãopor Cunha, Sara C.Outros Autores: Ferreira, Ricardo; Marmelo, Isa; Vieira, Luís R.; Anacleto, Patrícia; Maulvault, Ana et al.Origem: Repositório Institucional da UNLExposure of aquatic environments to emerging contaminants is a global issue, special relevant in many estuaries due to impacts from anthropogenic activity. The aim of this work was to evaluate thirty-seven endocrine disruptor chemicals (EDCs) from four different classes (pesticides, bisphenols, polycyclic musks and UV-filters) in water and sediment samples collected during one-year in the estuaries of Tagus and Douro Rivers located into the NE Atlantic Ocean coast. EDCs analysis was achieved afterward validation of a gas-chromatography mass spectrometry (GC–MS) method using Dispersive Liquid-Liquid Microextraction (DLLME) as extraction procedure for water samples, and Quick, Easy, Cheap, Efficient, Rugged and Safe (QuEChERS) combined with DLLME for sediments. Tagus estuary presented higher levels of contamination with pesticide residues and bisphenols (BPs) than the Douro estuary in both water and sediment samples. Contrariwise, levels and frequency of polycyclic musks (PCMs) and UV-filters (UVF) were slightly higher in Douro estuary. Levels of pesticide residues in both sediment and water samples, and levels of PCMs and UVF in water samples were higher in warmer seasons (summer and spring) than in colder ones (winter and autumn). The opposite was found in what respect levels of BPs in water and sediment samples, and PCMs and UVF levels in sediment samples. Although the levels found for each contaminant are low, usually in the order of a few ng/mL(g), the presence of a high number of toxic compounds is a source of concern and requires constant monitoring. -
10
De que é feito um império?
Publicaçãopor Varela, RaquelOutros Autores: Louçã, João CarlosOrigem: Repositório Institucional da UNLPortugal foi o império que mais utilizou, através de várias formas, o trabalho forçado, sistematicamente e por mais tempo. Realidade denunciada pela imprensa e agências internacionais, o trabalho forçado inseriu-se nos pilares da sociedade de que fazia parte: pobreza, inexistência de mobilidade social, separação familiar, agricultura de subsistência, extrema desigualdade de rendimentos e uma polícia política racista. Portugal was the empire that most used various forms of forced labour in the most systematic way and for the longest time. Widely denounced in the press and by international agencies, forced labour brought with it all the ailments of the society of which it was part: poverty, non-existence of social mobility, family break-ups, mere subsistence agriculture, extreme income inequality and a racist political police.
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