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In current days, the research in the photovoltaic field aims to find and investigate cheap thin-film materials based on earth-abundant element suitable for terawatt era. To this purpose Cu2ZnSnS4 (CZTS) has been widely studied in the last decade, being structurally analogous to the well-documented Cu(In,Ga)Se2 but featuring inexpensive and abundant components. Recently we have reported a simple and straightforward sol-gel process to produce CZTS-based solar cells demonstrating how it is possible to provide a working device with an easily transferable on an industrial scale and low cost process. In this work we report important improvements to the described above methodology by growing CZTS thin films on a transparent substrate aiming to produce bifacial solar cells suitable for an incorporation into a tandem solar cell architecture. The direct droplet deposition of the precursor ink onto the FTO substrate, leads to the kesterite phase. Gelation and annealing steps, without the addition of further sulphur sources make this procedure suitable for industrial scale-up saving a considerable amount of raw materials. UV–Vis absorption, μ-Raman, Photoluminescence, X-ray diffraction and Energy Dispersive Spectroscopy measurements have been performed on the so-produced thin films. The morphology of the samples has been investigated by scanning electron microscopy, proving the extremely good quality of the material. PV devices with a FTO/Mo/CZTS/CdS/ZnO/AZO architecture were obtained showing η = 1.11% in a bifacial set up. A lower η = 0.99% has been measured by illuminating the front side of the cell only, demonstrating that the bifacial setup allows a +11% efficiency enhancement.

The PV research is nowadays focused on finding low cost and easily processable thin-film materials, trying to move towards lighter and more versatile technologies. Among them, Cu2ZnSnS4 (CZTS) drew the attention of the scientific community thanks to its structural similarity to the already reported and well-studied Cu(In,Ga)Se2 but with the great advantage to use cheap and earth-abundant elements. In this work, we report CZTS-based solar cells produced with a simple and straightforward sol–gel process, demonstrating how further expensive and industrially non-scalable instruments are not needed in order to provide a working device. Direct drop-casting of a precursor solution onto the substrate, followed by gelation and final annealing in Ar atmosphere, generates the desired phase of the material without any further source of sulphur. The precursor solution contains metal acetate salts which play a primary role in networking the metals in the gel matrix, together with thiourea and dimethylsulfoxide. With this methodology, only the strictly necessary amount of reagents is used saving until 2–3 orders of magnitude of starting materials compared to other wet deposition techniques and working devices were obtained showing η = 1.1%. The addition of KCl as a dopant into the precursor solution was proven to be beneficial for the grain growth and material quality, so the performance of the corresponding devices rises it up to η = 1.75%. The synthesised thin films have been fully characterised by UV–Vis absorption, μ-Raman, X-ray diffraction and Energy Dispersive Spectroscopy measurements. Their morphology has been investigated by Scanning Electron Microscopy, proving the high quality of the material. The so-produced PV devices with a standard SLG/Mo/CZTS/CdS/ZnO/AZO architecture show interesting and promising results, especially in terms of short circuit current density.

Fine powders composed of tellurium grains of average size

Boosted by the simplicity of their synthesis and low toxicity, cholinium and amino acid-based ionic liquids have attracted the attention of researchers in many different fields ranging from computational chemistry to electrochemistry and medicine. Among the uncountable IL variations, these substances occupy a space on their own due to their exceptional biocompatibility that stems from being entirely made by metabolic molecular components. These substances have undergone a rather intensive research activity because of the possibility of using them as greener replacements for traditional ionic liquids. We present here a short review in the attempt to provide a compendium of the state-of-the-art scientific research about this special class of ionic liquids based on the combination of amino acid anions and cholinium cations.

Abstract Earth-abundant and non-toxic Kesterite-based Cu2ZnSnS4 (CZTS) thin film solar cells are successfully fabricated on flexible Molybdenum (Mo) foil substrates by an electrodeposition-annealing route. A well-adherent, densely packed, homogeneous, compact, and mirror-like CZT precursor is initially produced through electrodeposition by using a rotating working electrode. Subsequently, the co-electrodeposited CuZnSn (CZT) precursor is sulfurized in quartz tube furnace at 550 °C for 2 h in N2 atmosphere with the presence of elemental sulfur in order to form CZTS. Different characterization techniques like XRD, SEM, HR-TEM, Raman, and Photoluminescence demonstrate that almost phase-pure CZTS formed after sulfurization. A flexible Al/Al-ZnO/i-ZnO/CdS/CZTS/Mo foil solar cell is produced, where CdS is deposited by chemical bath deposition and transparent conducting oxide (TCO) is deposited by DC sputtering. The CZTS solar device shows a 0.55% power conversion efficiency on flexible Mo foil substrate and it constitutes the first prototype of this kind of solar cell produced by electrodeposition-annealing route without any surface modification of the Mo substrate. Graphic abstract

An analysis of the complex proton transfer processes in certain protic ionic liquids, based on amino acid anions, has been carried out through ab initio molecular dynamics in the view of finding naturally conductive and pure mediums. The systems analyzed here might serve as chemical prototypes for pure and dry ionic liquids where mobile protons can act as fast charge carriers. We have exploited the natural tendency of these liquids to form a complex network of hydrogen bonds. The presence of such a network allows the naturally repulsive interaction between like charge ions to be weakened to the point that a proton migration process inside the anionic component of the fluid becomes possible. We have also seen that the extent of these proton migrations is sizable for carboxylic based amino acid anions, while it is very limited for sulfur containing ones.

This chapter deals with the structural analysis of ionic liquid-containing mixtures through multiscale computational methods. The chapter is divided into two sections, dealing with a basic introduction to the topic, and a more in-depth presentation of four different computational methods typically used to simulate the structural and dynamical properties of complex liquid systems. Initially, the concept of the structure of a liquid is discussed, providing definitions and some examples. Subsequently, the main features of the experimental technique based on X-ray scattering are presented, which allow accessing structural information of amorphous systems. A short introduction of the laws governing the scattering phenomenon, and how scattered photons can provide information about the structure of a system is also presented. A significant part of this chapter is devoted to introducing four of the most used state-of-the-art computational methods, namely density functional theory “static” optimization, semiempirical molecular dynamics, classical molecular dynamics, and coarse-grained molecular dynamics. The starting point is the quantastic treatment of the system, in which only minimal approximations are used. The reader is then guided toward successive approximations enabling to explore different system sizes and timescales. The intricate system ethylammonium nitrate:acetonitrile 1:9 binary mixture is taken as a case study to show what the four obtained models can return in terms of characterization. The final picture describes how the various methods are fundamentally complementary to each other, meaning that there is nothing as a “best” method.

At the end of 2017 roughly 1.8% of the worldwide electricity came from solar photovoltaics (PV), which is foreseen to have a key role in all major future energy scenarios with an installed capacity around 5 TW by 2050. Despite silicon solar cells currently rule the PV market, the extremely more versatile thin film-based devices (mainly Cu(In,Ga)Se2 and CdTe ones) have almost matched them in performance and present room for improvement. The low availability of some elements in the present commercially available PV technologies and the recent strong fall of silicon module price below 1 $/Wp focused the attention of the scientific community on cheap earth-abundant materials. In this framework, thin film solar cells based on Cu2ZnSnS4 (CZTS) and the related sulfur selenium alloy Cu2ZnSn(S,Se)4 (CZTSSe) were strongly investigated in the last 10 years. More recently, chalcogenide PV absorbers potentially able to face TW range applications better than CZTS and CZTSSe due to the higher abundance of their constituting elements are getting considerable attention. They are based on both MY2 (where M = Fe, Cu, Sn and Y = S and/or Se) and Cu2XSnY4 (where X = Fe, Mn, Ni, Ba, Co, Cd and Y = S and/or Se) chalcogenides. In this work, an extensive review of emerging earth-abundant thin film solar cells based on both MY2 and Cu2XSnY4 species is given, along with some considerations on the abundance and annual production of their constituting elements.

We investigate low-temperature (&lt, 200 &deg, C) plasma-enhanced chemical vapor deposition (PECVD) for the formation of p&ndash, n junctions. Compared to the standard diffusion or implantation processes, silicon growth at low temperature by PECVD ensures a lower thermal budget and a better control of the doping profile. We previously demonstrated the successful growth of boron-doped epitaxial silicon layers (p+ epi-Si) at 180 &deg, C. In this paper, we study the activation of boron during annealing via dark conductivity measurements of p+ epi-Si layers grown on silicon-on-insulator (SOI) substrates. Secondary Ion Mass Spectroscopy (SIMS) profiles of the samples, carried out to analyze the elemental composition of the p+ epi-Si layers, showed a high concentration of impurities. Finally, we have characterized the p+ epi-Si layers by low-temperature photoluminescence (PL). Results revealed the presence of a broad defect band around 0.9 eV. In addition, we observed an evolution of the PL spectrum of the sample annealed at 200 &deg, C, suggesting that additional defects might appear upon annealing.

We present a computational analysis of the complex proton-transfer processes in two protic ionic liquids based on phosphorylated amino acid anions. The structure and the short time dynamics have been analyzed via ab initio and semi-empirical molecular dynamics. Given the presence of mobile protons on the side chain, such ionic liquids may represent a viable prototype of highly conductive ionic mediums. The results of our simulations are not entirely satisfactory in this respect. Our results indicate that conduction in these liquids may be limited due to a quick quenching of the proton-transfer processes. In particular, we have found that, while proton migration does occur on very short timescales, the amino groups act as proton scavengers preventing an efficient proton migration. Despite their limits as conductive mediums, we show that these ionic liquids possess an unconventional microscopic structure, where the anionic component is made by amino acid anions that the aforementioned proton transfer has transformed into zwitterionic isomers. This unusual chemical structure is relevant because of the recent use of amino acid-based ionic liquids, such as CO2 absorbent.

Nanosized clusters of protic ionic liquids are investigated using ab-initio DFT methods to understand their propensity to remain ionic. Protic ionic liquids are based on acid/base pairs and are ionic because of proton transfer from the acid to the base. Two prototypical ionic liquids based on triethylamine and two acids of different strengths are used here to trace the tendency toward proton transfer when the system size is gradually increased from an isolated pair of molecules to cluster of several pairs. We have found that the compounds based on the weak acid shows the existence of a well-defined minimal size that represents the threshold for the onset of ionization phenomena.

Open in a separate window The local structure of a series of homologous protic ionic liquids (PILs) is investigated using ab initio computations and ab initio-based molecular dynamics. The purpose of this work is to show that in PILs the network of hydrogen bonds may promote like-charge clustering between anionic species. We correlate the theoretical evidence of this possibility with viscosity experimental data. The homologous series of liquids is obtained by coupling choline with amino acid anions and varying the side chain. We find that the frictional properties of the liquids are clearly connected to the ability of the side chain to establish additional hydrogen bonds (other than the trivial cation–anion interaction). We also show that the large variation of bulk properties along the series of compounds can be explained by assuming that one of the sources of friction in the bulk liquid is the like-charge interaction between anions.

ZnS is a versatile, abundant and eco-friendly semiconductor material employed in many applications. In the present manuscript, ZnS thin films were grown by one of the most simple and scalable vacuum method, that is the room temperature radio frequency sputtering technique. An extensive characterization has been performed by atomic force microscopy, X-ray diffraction, absorption and photoluminescence spectroscopies to identify the growth conditions required to obtain compact and low- defective ZnS layers, as required in many applications. Optimized thin films consist of nanocrystalline ZnS with very low surface roughness with respect to the literature, which make them particularly suitable for optical interfacing and alternative buffer layer in chalcogenide thin film solar cells.

We explore the structure of a series of protic Ionic Liquids based on the choline cation and amino acid anions. In the series, the length and the branching of the amino acid alkyl chain varies. Ab initio molecular dynamics, X-ray diffraction measurements, and infrared spectra have been used to provide a reliable picture of the short-range structure and of the short-time dynamic process that characterize the fluids. We have put special emphasis on the peculiar and complicated network of hydrogen bonds that stem from the amphoteric nature of the anion moiety. The use of ab initio molecular dynamics allows us to calculate the “exact” charge density of the system and hence to obtain fairly accurate infrared spectra that, in turn, have been used to assign the experimental ones.

Ellagic acid (EA) and Annona Muricata (AM) have antioxidant, anticarcinogenic and antiviral activity demonstrated by in vitro models. This pilot study investigated the in vivo potential anti-viral activity in women affected by Low squamous intraepithelial lesion (L-SIL) related to high risk human papilloma virus (HR-HPV), and the ability to modify the oncoproteins expression in the cervical lesion thickness. Sixty women affected by HR-HPV related L-SIL, were randomly divided into two groups: group A (n = 30) supplemented with EA (16 mg) + AM (100 mg) 2 times daily for 6 months and group B (n = 30) administered with placebo. HR-HPV clearance was obtained in 74% of cases in group A compared to 25% of cases in group B (p = 0.001) and p21 expression in LSIL thickness increased in 63.2% of cases in group A compared to 20% in group B (p = 0.03). AE/AM supplementation significantly induces HR-HPV elimination and stimulates p21 expression in LSIL thickness.

In any crystallization process, convection rules the formation and distribution of impurities and precipitates. Silicon is actually a well studied material; however the distribution of impurities and their related precipitation processes are still not investigated from the point of view of diffusion and segregation phenomena. In principle, experimentation under microgravity can contribute to a better understanding of the processes occurring during solidification since the chemical segregation and distribution of impurities can be studied under purely diffusive transport conditions. In ground experiments, the effect of a reduced melt convection growth process and its effect on the crystal quality could be studied growing silicon by the Axial Heating Process (AHP). For this purpose, a modified Float Zone (FZ) technique using an additional AHP heater submerged into the melt was applied in this work to grow silicon single crystal. The obtained samples were inspected by resistivity measurements and spectroscopic techniques (PL, FT-IR). The spatial distribution of the dopant along the ingot obtained by local resistivity measurements was compared with a theoretical distribution of dopant. PL measurements confirm the high quality level of the grown ingots and infrared spectroscopy reveals low carbon and oxygen concentration. Such an approach seems to be very promising also for solar grade Si solidification for PV applications.

It is widely known that photoluminescence (PL) and infrared (IR) spectroscopies are among the experimental tools extensively used in the last decades for the study of impurities and defects in silicon for both microelectronic and photovoltaic applications. This review paper reports the main historical achievements and recent developments obtained in this field by PL and IR, paying particular attention to the most useful data for the study of defects in silicon for photovoltaic applications. © 2014 Elsevier B.V. All rights reserved.

Owing to the very brittle nature of the tellurium powder, nanoscopic grains with average size of 4.8nm were produced by dry vibration milling technique using a Mixer mill apparatus. A novel material was obtained by binding the nanosized tellurium grains with poly(methyl methacrylate) (PMMA). The morphology, elemental composition, and structural properties of Te/PMMA films were investigated. The prepared material was composed of hexagonal tellurium and α-phase of tellurium oxide. The electrical properties of the films were studied in dark condition and under white light illumination varying the optical power density from 10 to 170 mW/cm2 and turning on and off the light cyclically.

Cu2ZnSnS4 (CZTS) thin films and solar cells were successfully prepared using a new process based on spray pyrolysis technique. The main advantage of the proposed process is the avoiding of sulphurisation process at high temperature and in toxic gases like H2S. X-ray diffraction studies and Raman spectroscopy confirmed the formation of good-quality microcrystalline CZTS films in a tetragonal structure. Optical measurements showed that CZTS films have a direct band gap and high absorption coefficient (4 × 104 cm−1) as requested for solar cell application. CZTS solar cell prototypes deposited on low-cost flexible plastic substrates were prepared and tested.

In the thin film solar cells domain, copper indium galium (di)selenide (CIGS) is a material with well-established photovoltaic purpose. Here the presence of a suitable [Ga]/([Ga]+[In]) (GGI) in-depth profile has proved to play a key role in the performance of cells. The implementation of a routine method based on reliable but easily available experimental techniques is mandatory to obtain information on the GGI profile of any CIGS layer, in order to achieve high efficiency chalcogenide layers. In this vein, we here propose and systematically test a simple method for the GGI profile determination based on repeated bromine etching of CIGS thin films followed by Raman analysis of the A1 peak position. The reliability of the proposed approach is verified using a methodical comparison with energy-dispersive X-ray spectroscopy (EDS) analysis and secondary ion mass spectroscopy (SIMS) profiles, showing a good agreement with the GGI in-depth profiles determined using Raman analysis on bromine etched samples.

We have recently shown that some protic ionic liquids (PILs) are characterized by an unexpected complex dynamic of proton transfer (M. Campetella et al., Phys. Chem. Chem. Phys. 19, 11,869, (2017)). These liquids are based on a combination of cholinium cations and amino acid (AA) deprotonated anions. The side chain proton migration, can take place both within the same anion and between different anions. The intra-molecular proton transfer leads to a tautomerization of the AA anion that gives rise to the appearance of an anionic zwitterionic form. The inter-molecular proton transfer is chemically more interesting since it might, at least in principle, point to a way to achieve a dry, fast conduction in materials that are otherwise very viscous and typically poor conductors. We examine here, by means of ab-initio computations, the basic mechanism of proton transfer in a variety of AA anions to find promising candidates as new materials for electrochemistry applications.

Today, after more than 70 years of continued progress on silicon technology, about 85% of cumulative installed photovolatic (PV) modules are based on crystalline silicon (c-Si). PV devices based on silicon are the most common solar cells currently being produced, and it is mainly due to silicon technology that the PV has grown by 40% per year over the last decade. An additional step in the silicon solar cell development is ongoing, and it is related to a further efficiency improvement through defect control, device optimization, surface modification, and nanotechnology approaches. This paper attempts to briefly review the most important advances and current technologies used to produce crystalline silicon solar devices and in the meantime the most challenging and promising strategies acting to increase the efficiency to cost/ratio of silicon solar cells. Eventually, the impact and the potentiality of using a nanotechnology approach in a silicon-based solar cell are also described.

In the present work, Kesterite-Cu2ZnSnS4 (CZTS) thin films were successfully synthesized from stacked bilayer precursor (Zn/Cu-Sn) through electrodeposition-annealing route. Adherent and homogeneous Cu-poor, Zn-rich stacked metal Cu-Zn-Sn precursors with different compositions were sequentially electrodeposited, in the order of Zn/Cu-Sn onto Mo foil substrates. Subsequently, stacked layers were soft annealed at 350 °C for 20 min in flowing N2 atmosphere in order to improve intermixing of the elements. Then, sulfurization was completed at 585 °C for 15 min in elemental sulfur environment in a quartz tube furnace with N2 atmosphere. Morphological, compositional and structural properties of the films were investigated using SEM, EDS and XRD methods. Raman spectroscopy with two different excitation lines (514.5 and 785 nm), has been carried out on the sulfurized films in order to fully characterize the CZTS phase. Higher excitation wavelength showed more secondary phases, but with low intensities. Glow discharge optical emission spectroscopy (GDOES) has also been performed on films showing well formed Kesterite CZTS along the film thickness as compositions of the elements do not change along the thickness. In order to investigate the electronic structure of the CZTS, Photoluminescence (PL) spectroscopy has been carried out on the films, whose results matched up with the literatures.

Self-organized surface structures were produced by picosecond laser pulses on multi-crystalline silicon for photovoltaic applications. Three different laser wavelengths were employed (i.e. 1064 nm, 532 nm and 355 nm) and the resulting morphologies were observed to effectively reduce the reflectivity of the samples after laser irradiation. Besides, a comparative study of the laser induced subsurface damage generated by the three different wavelengths was performed by confocal micro-Raman, photoluminescence and transmission electron microscopy. The results of both the structural and optical characterization showed that the mc-Si texturing performed with the laser at 355 nm provides surface reflectivity between 11% and 8% over the spectral range from 400 nm to 1 μm, while inducing the lowest subsurface damage, located above the depletion region of the p – n junction.

The effects of vitamin D concentrations on bone mineral content in adolescents are still unclear. Vitamin D and physical activity (PA) may interact to determine bone mineral content (BMC) in two possible directions; 25(OH)D sufficiency levels improve BMC only in active adolescents, or PA increases BMC in individuals with replete vitamin D levels. The effects of suboptimal 25-hydroxycholecalciferol (25(OH)D) concentrations on BMC in adolescents are still unclear. The main aim of this study was to evaluate the influence of 25(OH)D on BMC in adolescents, considering the effect of body composition, sex, age, Tanner stage, season, calcium and vitamin D intakes, physical fitness and PA. Serum 25(OH)D concentrations, anthropometric measurements, dual energy X-ray absorptiometry measurements, calcium and vitamin D intakes, PA and physical fitness were obtained in 100 Spanish adolescents (47 males), aged 12.5–17.5 years, within the framework of the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study. Relations were examined using ANCOVA and regression analyses including BMC as dependent variable. Linear regression of BMC suggested that 25(OH)D concentrations independently influenced total and leg BMC after controlling for age, sex, lean mass, seasonality and calcium intake (B = 0.328, p

Background: An adequate nutritional status of antioxidant vitamins (vitamins A, C, E) and β-carotene is essential especially during childhood and adolescence, because of their important roles in cell growth and development. Currently, there are no physiological reference values for blood concentration of these vitamins and β-carotene in apparently healthy European adolescents. The aim of the current study was to obtain reliable and comparable data of antioxidant vitamins and β-carotene in a cross-sectional study, within HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence), which was conducted in a representative sample of adolescents from ten European cities. Material and Methods: From a subsample of 1,054 adolescents (males= 501) of the HELENA Cross Sectional Study with an age range of 12.5 to 17.49 years, fasting blood samples were taken and analyzed for vitamins A, E, C, and β-carotene status. As specific reference values for adolescents are missing, percentile distribution by age and sex is given. Results: Mean concentrations were the following: Retinol: 356.4 ± 107.9 cm/mL; α-tocopherol: 9.9 ± 2.1 μg/mL; vitamin C: 10.3 ± 3.3 mg/L; and β-carotene: 245.6 ± 169.6 cm/mL. Females showed higher α-tocopherol and vitamin C values compared with males and 17-year-old boys had higher retinol levels than the same-aged girls (p = 0.018). Retinol serum concentrations increased significantly according to age in both gender, but girls had also significantly increasing β-carotene levels by age. Conclusions: For the first time, concentrations of antioxidant vitamins and pro-vitamin β-carotene have been obtained in a representative sample of apparently healthy European adolescents. These data can contribute to the establishment of reference ranges in adolescents. © 2011 Hans Huber Publishers, Hogrefe AG, Bern.

This paper reports results about aluminium gallium indium phosphide (AlGaInP) based solar cells, in order to define their physical properties for applications in high efficiency devices. In fact, used as top junction, AlGaInP is a promising material for the realization of high efficiency solar cells with more than three junctions. Here AlGaInP single junction solar cells grown on germanium substrates with aluminium concentration varying from 0% to 12% were studied in detail by optical and electrical methods. © 2010 Elsevier B.V. All rights reserved.

Background/Aims: The assessment of bone mineral content (BMC) and density (BMD) status in children and adolescents is important for health and the prevention of diseases. Bone metabolic activity could provide early information on bone mass development. Our aim was to describe bone mass and metabolism markers according to age and Tanner stage in adolescents. Methods: Spanish adolescents (n = 345; 168 males and 177 females) aged 12.5–17.5 years participated in this cross-sectional study. Body composition variables were measured by dual-energy X-ray absorptiometry. Serum osteocalcin (n = 101), aminoterminal propeptide of type I procollagen (n = 92) and β-isomerized C-telopeptides (β-CTX, n = 65) and urine samples (β-CTX; n = 237) were analyzed by electrochemiluminescence immunoassay. Results: Analysis of covariance showed that females had higher values for BMC and BMD in most of the regions. Both males and females had a significant decrease in bone markers while sexual maturation increases (all p < 0.05). Males had an increased bone turnover compared to females (all p < 0.05, except for urine β-CTX in Tanner ≤IV). Conclusion: Our results support the evidence of dimorphic site-specific bone accretion between sexes and show an increased bone turnover in males, suggesting higher metabolic activity.

Multicrystalline Silicon was textured with picosecond laser. Different laser wavelengths (λ = 1064, 532, 355 nm) where compared regarding laser-induced damage. We found that λ = 355 nm picosecond radiation resulted in shallower defect-reach region. © 2015 OSA

Electrodeposition followed by sulfurization could be a favourable process for the fabrication of the CZTS thin film solar cells. Here we attempt to fabricate CZTS thin films from co-electrodeposited precursors of Cu-Zn-Sn with various compositions from Cu-poor, Zn-rich to Cu-rich, Zn-poor. Different characterization methods like XRD, SEM (EDS), and Raman spectroscopy have been employed to investigate the structure, morphology, and composition as well as the precursor compositional effect on the final sulfurized films. From the results, by electrodeposition it is possible to form a good crystalline form of Kesterite CZTS with the help of precise control of precursor compositions (Cu-poor, Zn-rich) in order to overcome the volatility effect of Zn and Sn during annealing at high temperature.

Cu2ZnSnS4(CZTS) absorber layers grown by sputtering were investigated by photoluminescence before and after the chemical bath deposition of CdS in order to evaluate the possible passivation of point defects by Cd atoms at the absorber/buffer layer interface. According to the literature, a broad emission around 1.21 eV was observed at low temperature under above bandgap excitation of the as-grown CZTS samples. Broad bands at 1.075 eV and 0.85 eV were detected for the first time under below bandgap excitation of the as-grown CZTS samples at low temperature, which were explained in terms of radiative transitions involving point defect-related levels determined in the literature by first-principles calculations. The emissions observed in the as-grown samples were monitored by both above and below bandgap excitations also in standard CZTS solar cells produced on the same layers. The obtained results suggest that, as in the case of Cu(In, Ga)Se2, Cd atoms passivate point defects at the absorber/buffer layer interface also in CZTS.

The analysis of the photoluminescence (PL) spectra of a number of silicon samples plastically deformed or simply thermally annealed was used to understand the rol e of oxygen and oxygen precipitates on the PL emissions in the 0.8-1.0 eV range. The results of this analysis show that it is possible to discrim inate between emissions due to oxygen-associated centres and those due to dislocations. Furthermore, i t has been shown on a sample presenting only (dissociated) 60° dislocations that the 0.807 eV e mission is absent, demonstrating that it comes either from dislocation intersections or from scr ew segments. Finally, it has been suggested that the strain field associat ed to oxide precipitates might be responsible of both narrow and broad bands, systematically present in most of the samples examined, which are therefore interpreted as being due to carr ier confinement effects in localized quantum wells at silicon/silicon oxide interfaces of oxide precipitates.

Flavouring substances may be naturally present in a food and/or intentionally added. It is essential to have a method to estimate exposure that is rapidly performed and does not underestimate exposure. Recently, a new approach for flavouring, the “Added Portions Exposure Technique” (APET), was proposed by the European Food Safety Authority. This paper explains step by step this technique using furaneol as case study. APET's main advantage is that it allows the assessment of dietary exposure in adults, children and infants, from both added flavourings and from flavourings naturally contained in food, and considering both acute and chronic exposure.

Silicon rich hydrogenated amorphous silicon-carbon alloy films were deposited by plasma enhanced chemical vapour deposition in low power regime from silane methane mixtures diluted in helium by varying the methane fraction between 0.4 and 0.8. Films with carbon content ranging from 0.06 to 0.28 were obtained with a deposition rate of about 0.1 nm/s. The influence of carbon incorporation on the optical properties as well as disorder and defect density of the films has been investigated. The increase in carbon content leads to a decrease of the refractive index and an increase of the optical gap and disorder in the films. The defect density also increases with increasing carbon content, however lower values than those of films deposited by undiluted silane methane mixtures have been obtained for a carbon content greater than 0.1. Finally, the enhancement of carbon content causes the shift of peak position as well as the increase in the intensity and the width of the photoluminescence spectra. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

p-doped hydrogenated nanocrystalline silicon (p-nc-Si:H) is one of the most critical layers in thin film silicon solar cells. LEPECVD is a new technique for the growth of nc-Si at high growth rate without compromising the layer quality, using a dense but low energy plasma. Thin p-nc-Si:H layers are grown on glass and ZnO:Al coated glass and their structural and electrical properties are investigated as a function of the silane dilution (d) and of the doping ratio (DR). The influence of the substrate on the structural properties is investigated and discussed. The incubation layer is clearly observed on both substrate types and its thickness is estimated. LEPECVD distinguishes itself from other high growth rate methods by a very low impurity distribution coefficient to obtain a comparable conductivity and boron density. The conduction path is shown to be dependent on the density of boron in the layer while a significant decrease of conductivity at high DR is not observed in the studied range (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper crucial factors for the deposition of AZO/i-ZnO bi-layers to be used as front contact in chalcogenide photovoltaics are considered, with emphasis on effect of the deposition parameters on the electrical and optical properties. Thereby, a systematic study focused on the substrate temperature, substrate to target distance and i-ZnO and AZO thickness has been performed with the aim of scaling up the deposition processes on large areas. The transmittance of the AZO/i-ZnO/glass thin film bi-layer structure resulted between 85% and 92%. Moreover, while the increase of the i-ZnO film thickness hinders the bi-layer electrical properties, they were found to be improved with increasing AZO thickness. This phenomenon can be assigned to the increase of the grain size in the thickest films that reduces the grain boundary scattering. A figure of merit, expressed as ratio of the logarithm of the transmittance T r (average value in the 400-800 nm wavelength) to the resistivity ρ of the films, as high as 22700 Ω-1 cm-1 was obtained for the deposition performed at a substrate temperature of 150 °C. This figure of merit was obtained on the basis of a resistivity value of 4.84×10-4 Ω cm and a transmittance of 91% in the visible range. Therefore the results obtained in this work on large substrates match the requirements for high quality optical and photovoltaic applications. © 2014 Elsevier Ltd and Techna Group S.r.l.

Ordered mesoporous silica nanoparticles (MSNs) were impregnated with different loadings of the luminescent complex tris(dibenzoylmethane) mono(1,10-phenanthroline)europium(III) (Eu(dbm) 3 phen), with the aim of increasing the luminescence by avoiding concentration quenching and having mainly in mind the application as spectral converter for multi-crystalline silicon solar cells. The morphological, structural and luminescence properties of the impregnated silica nanoparticles were characterized by N 2 physisorption, X-ray diffraction, transmission electron microscopy, infrared spectroscopy, UV–visible spectroscopy and photoluminescence excitation and emission measurements. Photostability was tested under 1 sun (1000 W/m 2 ) illumination for 24 h and the related effects were inspected by UV–visible and photoluminescence spectroscopies. Impregnation of the complex into 50–70 nm MSNs with pore size tailored around 2.9 nm depressed concentration quenching and allowed the use of complex loadings as high as 23 wt%. Sunlight irradiation caused a marked increase in the luminescence intensity.

Background and aims Italian National Food Consumption Survey, INRAN-SCAI 2005–06, is the third national food consumption survey performed in Italy. This study describes energy and nutrient intakes in Italy. Methods and results A national cross-sectional food consumption survey was conducted using consecutive 3-day food records between October 2005 and December 2006. A sample of 3323 males and females aged 0.1–97.7 years living in private households was investigated. Individual food records were converted into energy and nutrient intakes with the use of recently updated national food composition databases. For each subject, intakes of energy and of 27 nutrients were calculated, including six minerals (i.e., iron, calcium, phosphorus, magnesium, potassium and zinc) and 10 vitamins (i.e., thiamine, riboflavin, vitamin C, vitamin B 6 , retinol, β-carotene, vitamin A as retinol equivalents (REs), vitamin E, vitamin D and vitamin B 12 ). On average, 36% of calories appeared to derive from fat (11% from saturated fatty acids) and 45% from available carbohydrates (15% from soluble carbohydrates). Conclusions The results of the INRAN-SCAI 2005–06 survey in terms of nutrient intakes provide an important piece of information for nutrition surveillance of the population and may also be used to identify priorities for further research.

International audience; AIM: To compare different methods of assessing dietary exposure to flavourings in the context of a stepwise approach. METHODS: The dietary exposure to four flavourings was determined: raspberry ketone, glycyrrhizinic acid, coumarin, and caffeine. When dietary exposure exceeded the safety limits, the need for more detailed assessment using less aggregated data was judged necessary. First, screening methods (Maximized Survey-Derived Daily Intake - MSDI, Single-Portion Exposure Technique - SPET and modified Theoretical Added Maximum Daily Intake - mTAMDI) were applied. Next, individual food consumption data were used for creating models with different levels of detail to identify the foods: a model based on food groups and models based on food items. Three food item models were developed: without improvements of the flavouring descriptor built in the software; with improvements; with use of non-specified flavour descriptors. Consumption data were collected from 121 Dutch adults using a computerized 2x24h-dietary recall (EPIC-Soft) in the European Food Consumption Validation (EFCOVAL) study. RESULTS: Based on results of at least one of the three screening methods, refined assessment was necessary for raspberry ketone, glycyrrhizinic acid and caffeine. When applying the food group model, the need of refinement was indicated for the four flavourings. When applying the food item models, only glycyrrhizinic acid and caffeine presented dietary exposure above the safety limits. In the raspberry ketone case, dietary exposure increased when improvements in food description were considered. The use of non-specified flavour descriptors hardly changed the results. CONCLUSION: The collection of detailed food consumption data at the individual level is useful in the dietary exposure assessment of these flavourings.

This paper reports the electrical characterization of commercially available crystalline silicon solar cells encapsulated with poly-vinylacetate doped with different Eu3+ organic complexes. The inclusion of these complexes in the encapsulating matrix allows down-shifting of the solar spectrum components below 420 nm toward the maximum quantum efficiency of the solar cells. This effect has been proven under Air Mass 1·5 conditions (simulating terrestrial applications) where an increase of the total power delivered by the encapsulated cells has been observed. Moreover, this enhancement has been obtained using very low percentage by weight of organolanthanide dopants, allowing a reduction in the Watt peak price. At higher concentrations a strong quenching of the energy transfer from the organic antenna to the lanthanide ion has been observed. Copyright © 2009 John Wiley & Sons, Ltd.

Cu 2 ZnSnS 4 (CZTS) thin films were grown with a two-step process. Metal precursors deposited on Mo-coated soda lime glasses by RF sputtering were sulphurised by thermal treatment in sulphur vapours. To optimise the growth process, comprehensive structural characterisation (by electron microscopy, Raman spectroscopy and X-ray diffraction) of the CZTS films was mandatory. The results are reported and discussed herein. Of the many stoichiometries obtained by sulphurisation, Cu-poor/Zn-rich CZTS films were chosen as absorber layers to be tested in photovoltaic devices in order to prevent development of the Cu 2 − x S secondary phase typical of Cu-rich samples. Electrical characterisation of these CZTS solar cells demonstrates efficiency around 4%.

Objective: The present study assessed whether compliance with the Food-Based Dietary Guidelines is related to habitual fatty acid (FA) intake and blood lipid parameters. Methods: Dietary information was collected by two non-consecutive 24-h recalls in 1804 European adolescents. Compliance with the Food-Based Dietary Guidelines was expressed by calculating the Diet Quality Index for Adolescents (DQI-A). Blood samples were collected in a randomly selected subset (n = 552). Relations between FA intake/serum concentrations and DQI-A were tested with multilevel regression analysis to correct for the study design (clustering within cities). Analyses were stratified for gender; age was entered as a covariate. Results: Better DQI-A scores were related to increased proportional intakes of energy from total fat, saturated FA, monounsaturated FA, and cholesterol (P < 0.001), whereas no significant association was observed with polyunsaturated FA intakes. In adolescents with higher compared with lower DQI-A scores, dairy products contributed more (21.0% versus 12.7%) and low-nutrient, energy-dense items contributed less (17.2% versus 26.3%) to the intake of total fat. A positive association was observed between the DQI-A scores and serum concentrations of eicosapentaenoic acid and docosahexaenoic acid (all P < 0.005). The latter, however, was significant only in girls. In boys, higher DQI-A scores were inversely associated with serum cholesterol concentrations (P < 0.05). Conclusion: Although compliance with the Food-Based Dietary Guidelines was not always associated with a favorable FA intake pattern, a significant favorable association with some serum biomarkers was observed. This outcome underlines the importance of considering dietary habits instead of single-nutrient intakes. © 2013 Elsevier Inc.

In n-type Czochralski silicon (Cz-Si) wafer, swirl shaped regions with low lifetime (known as striations) can cause degradation up to 1% absolute or even more in homojunction industrial solar cells. Nevertheless, the nature of the defects responsible for the occurrence of these striations is still unclear. In this work, n-type Cz-Si solar cell precursors cut from industrial size ingots with different feedstock quality and oxygen content were analyzed by microwave photo-conductance decay and photoluminescence in order to investigate the nature of such defects. The results demonstrate that the defects responsible for the occurrence of striations are oxide nanoprecipitates formed during the high temperature steps for the solar cell realization, due to the presence of grown-in oxygen nuclei.

The atomic structure of large agglomerates of interstitials in silicon crystals, i.e. rod-like defects (RLD), was extensively investigated previously using transmission electron microscopy (TEM) methods. Much less is known about electronic properties of these defects. The electric-dipole spin resonance (EDSR) signals and photoluminescence (PL) spectra from Si samples with RLDs allow investigation of electronic properties and formation-evolution peculiarities of these defects. Obtained results clearly show qualitative evolution of the EDSR signals from RLDs with annealing time. Namely, new signals with modified symmetry are formed upon annealing and that detected at earlier stages of annealing – disappear. Comparison of the EDSR results with published TEM data allows determination of atomic structures related to distinct EDSR signals. Correlations of the EDSR signals and peculiarities in the PL spectra for the similar samples are reported. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Photovoltaics is the most promising technology for the future of green energy production. To fully realize the potential use of photovoltaic technology, low manufacturing cost and high working photoconversion efficiency must be obtained. Light trapping by metal nanoparticles is an attractive strategy in thin film as well as in bulk silicon solar cells aimed to confine light within the active layer to promote the photon absorption and therefore achieving higher efficiency. In this paper, we tested the deposition of silver and gold nanoparticles on bulk silicon solar cells by colloidal technique in order to enhance their photovoltaic conversion efficiency by means of Plasmonic Light Scattering by metal nanoparticles. The feasible Plasmonic Light Scattering related enhancement was examined using spectral response and I – V measurements. Relative increases of the total delivered power under simulated solar irradiation were observed for cells both with and without antireflection coating using silver and gold nanoparticles.

In a previous study, Italian female teenagers regular consumers of sugar free soft drinks and table-top sweeteners were suggested to have a higher intake of intense sweeteners than other teenagers. A food frequency questionnaire designed to identify adolescents who were high consumers of these food products was filled in by a randomly extracted sample of teenagers (n=3982) living in the District of Rome (Italy) in year 2000. A consumer survey was then carried out in a randomly extracted sub-sample of males and females and in all females who reported high consumption of sugar-free soft drinks and/or table-top sweeteners. A total of 362 subjects participated in a detailed food survey by recording, at brand level, all foods and beverages ingested over 12 days. For each sugar-free product, producers provided the concentration of intense sweeteners (saccharin, aspartame, acesulfame K and cyclamate). No intake in excess of the Acceptable Daily Intake (ADI) was observed. Also medicines and supplements were taken into account and these did not result in a large impact on chronic exposure to intense sweeteners. The intake levels did not exceed the ADI even under a worst case scenario which was performed to take into consideration a hypothetical future substitution of all regular food products with their sugar-free version. It can be concluded that, with the observed current consumption patterns and occurrence levels, the risk of an excessive intake of intense sweeteners by Italian teenagers is extremely low.

An adequate vitamin D status is essential during childhood and adolescence, for its important role in cell growth, skeletal structure and development. It also reduces the risk of conditions such as CVD, osteoporosis, diabetes mellitus, infections and autoimmune disease. As comparable data on the European level are lacking, assessment of vitamin D concentrations was included in the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study. Fasting blood samples were obtained from a subsample of 1006 adolescents (470 males; 46·8 %) with an age range of 12·5–17·5 years, selected in the ten HELENA cities in the nine European countries participating in this cross-sectional study, and analysed for 25-hydroxycholecalciferol (25(OH)D) by ELISA using EDTA plasma. As specific reference values for adolescents are missing, percentile distribution were computed by age and sex. Median 25(OH)D levels for the whole population were 57·1 nmol/l (5th percentile 24·3 nmol/l, 95th percentile 99·05 nmol/l). Vitamin D status was classified into four groups according to international guidelines (sufficiency/optimal levels ≥ 75 nmol/l; insufficiency 50–75 nmol/l; deficiency 27·5–49·99 nmol/l and severe deficiency P