Band-gap engineering of Cu2ZnSn1-xGe xS4 single crystals and influence of the surface properties

Thin film solar cells based on Cu2ZnSn(S,Se)4 are very promising, because they contain earth-abundant elements and show high absorptivity. However, the performance of these solar cells needs to be improved in order to reach efficiencies as high as that reported for Cu(In,Ga)Se 2-based devices. This study investigates the potential of band-gap engineering of Cu2ZnSn1-xGexS 4 single crystals grown by chemical vapour transport as a function of the [Ge]/([Sn] + [Ge]) atomic ratio. The fundamental band gap E0 is found to change from 1.59 to 1.94 eV when the Ge content is increased from x = 0.1 to x = 0.5, as determined from spectroscopic ellipsometry measurements. This knowledge opens a route to enhancing the performance of kesterite-based photovoltaic devices by a Ge-graded absorber layer. Furthermore, the formation of GeO2 on the surface of the as-grown samples was detected by X-ray photoelectron spectroscopy, having an important impact on the effective optical response of the material. This should be also taken into account when designing photovoltaic solar cellsRC acknowledges financial support from Spanish MINECO within the program Ramón y Cajal (RYC-2011-08521). This work was supported by the Marie Curie-IRSES project (PVICOKEST, GA: 269167), MINECO projects (KEST-PV, ENE2010-21541-C03-01/-02/-03) and Marie Curie-ITN project (KESTCELL, GA: 316488

An evaluation of seismic hazard in La Hispaniola, after the 2010 Haiti earthquake

An evaluation of the seismic hazard in La Hispaniola Island has been carried out, as part of the cooperative project SISMO-HAITI, supported by the Technical University of Madrid (UPM) and developed by several Spanish Universities, the National Observatory of Environment and Vulnerability) ONEV of Haiti, and with contributions from the Puerto Rico Seismic Network (PRSN) and University Seismological Institute of Dominican Republic (ISU). The study was aimed at obtaining results suitable for seismic design purposes. It started with the elaboration of a seismic catalogue for the Hispaniola Island, requiring an exhaustive revision of data reported by more than 20 seismic agencies, apart from these from the PRSN and ISU. The final catalogue contains 96 historical earthquakes and 1690 instrumental events, and it was homogenized to moment magnitude, Mw. Seismotectonic models proposed for the region were revised and a new regional zonation was proposed, taking into account geological andtectonic data, seismicity, focal mechanisms, and GPS observations. In parallel, attenuation models for subduction and crustal zones were revised in previous projects and the most suitable for the Caribbean plate were selected. Then, a seismic hazard analysis was developed in terms of peak ground acceleration, PGA, and spectral accelerations, SA (T), for periods of 0.1, 0.2, 0.5, 1 and 2s, using the Probabilistic Seismic Hazard Assessment (PSHA) methodology. As a result, different hazard maps were obtained for the quoted parameters, together with Uniform Hazard Spectra for Port au Prince and the main cities in the country. Hazard deaggregation was also carried out in these towns, for the target motion given by the PGA and SA (1s) obtained for return periods of 475, 975 and 2475 years. Therefore, the controlling earthquakes for short- and long-period target motions were derived. This study was started a few months after the 2010 earthquake, as a response to an aid request from the Haitian government to the UPM, and the results are available for the definition of the first building code in Haiti

Wide band-gap tuning Cu2ZnSn1-xGexS4 single crystals: optical and vibrational properties

The linear optical properties of Cu2ZnSn1-xGexS4 high quality single crystals with a wide range of Ge contents (x = 0.1, 0.3, 0.5, 0.7, 0.9 and 1) have been investigated in the ultraviolet and near infrared range using spectroscopic ellipsometry measurements. From the analysis of the complex dielectric function spectra it has been found that the bandgap E0 increases continuously from 1.49 eV to 2.25 eV with the Ge content. Furthermore, the evolution of the interband transitions E1A and E1B has been also determined. Raman scattering using three different excitation wavelengths and its analysis have been performed to confirm the absence of secondary phases in the samples, and to distinguish between stannite, wurtzite, wurzstannite and kesterite structures. Additionally, the analysis of the high resolution Raman spectra obtained in samples with different [Ge]/([Ge]+[Sn]) ratios allows describing a bimodal behavior of the dominant A modes. The understanding of the incorporation of Ge into the Cu2ZnSnS4 lattice is fundamental in order to develop efficient bandgap engineering of these compounds towards the fabrication of kesterite based solar cells with enhanced performanc

Spectroscopic ellipsometry study of Cu2ZnSnS4 bulk poly-crystals

The linear optical properties of Cu2ZnSnS4 bulk poly-crystals have been investigated using spectroscopic ellipsometry in the range of 1.2-4.6 eV at room temperature. The characteristic features identified in the optical spectra are explained by using the Adachi analytical model for the interband transitions at the corresponding critical points in the Brillouin zone. The experimental data have been modeled over the entire spectral range taking into account the lowest E0 transition near the fundamental absorption edge and E1A and E1B higher energy interband transitions. In addition, the spectral dependences of the refractive index, extinction coefficient, absorption coefficient, and normal-incidence reflectivity values have been accurately determined and are provided since they are essential data for the design of Cu2ZnSnS4 based optoelectronic devicesThe research leading to the presented results was partially supported by the European Project INFINITE-CELL (Ref. H2020-MSCA-RISE-2017-777968, 2017–2021, www.infinitecell.eu) and the Spanish MINECO Projects “WINCOST” (ENE2016-80788-C5-2-R) and PHOTOMANA (TEC2015- 69916-C2-1-R). The authors from the Institute of Applied Physics appreciate the financial support from STCU 6224 and from the Institutional Project No. CSSDT 15.817.02.04

Short and long-term experiments on the effect of sulphide on microalgae cultivation in tertiary sewage treatment

[EN] Microalgae cultivation appears to be a promising technology for treating nutrient-rich effluents from anaerobic membrane bioreactors, as microalgae are able to consume nutrients from sewage without an organic carbon source, although the sulphide formed during the anaerobic treatment does have negative effects on microalgae growth. Short and long-term experiments were carried out on the effects of sulphide on a mixed microalgae culture. The short-term experiments showed that the oxygen production rate (OPR) dropped as sulphide concentration increased: a concentration of 5 mg S L¿1 reduced OPR by 43%, while a concentration of 50 mg S L¿1 came close to completely inhibiting microalgae growth. The long-term experiments revealed that the presence of sulphide in the influent had inhibitory effects at sulphide concentrations above 20 mg S L¿1 in the culture, but not at concentrations below 5 mg S L¿1. These conditions favoured Chlorella growth over that of Scenedesmus.This research work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO, CTM2011-28595-C02-01 and CTM2011-28595-C02-02) jointly with the European Regional Development Fund (ERDF), both of which are gratefully acknowledged. It was also supported by the Spanish Ministry of Education, Culture and Sport via a pre doctoral FPU fellowship to author J. Gonzalez-Camejo (FPU14/05082) and by the Spanish Ministry of Economy and Competitiveness via a pre doctoral FPI fellowship to author R. Serna-Garcia (project CTM2014-54980-C2-1-R)Gonzalez-Camejo, J.; Serna-Garcia, R.; Viruela Navarro, A.; Paches Giner, MAV.; Durán Pinzón, F.; Robles Martínez, Á.; Ruano García, MV.... (2017). Short and long-term experiments on the effect of sulphide on microalgae cultivation in tertiary sewage treatment. Bioresource Technology. 244:15-22. https://doi.org/10.1016/j.biortech.2017.07.126S152224

Building Conventional Metasurfaces with Unconventional Interband Plasmonics: A Versatile Route for Sustainable Structural Color Generation Based on Bismuth

This is the final version. Available on open access from Wiley via the DOI in this recordData Availability Statement: The data that support the findings of this study are available in the supplementary material of this article.Plasmonic metasurfaces for structural color generation are typically built using the archetypal noble metals, gold, and silver. These possess plasmonic properties in the visible spectrum due to their inherent high free carrier densities. However, they are much more expensive compared to many other metals and exhibit several nanofabrication issues such as bad surface adhesion or thermally activated inter-diffusion. In this work, it is shown that interband plasmonic materials –whose optical properties are driven by interband transitions instead of free carriers— are appealing candidates for the fabrication of sustainable and cost-efficient metasurfaces for structural coloring. By using bismuth, an environment-friendly interband plasmonic material cheaper than gold and silver, nanodisks gap-plasmon metasurfaces and planar Fabry-Perot cavities are modeled and fabricated, which both successfully enable pure colors that can be robustly tailored upon suitable design. By direct experimental comparison between both types of design in terms of color efficiency, fabrication complexity, and angular robustness; how bismuth-based gap surface plasmon metasurfaces can be excellent candidates for color microprinting is shown, whereas nanolayered Bi Fabry-Pérot cavities are ideal for macroscopic color coatings due to their ease of fabrication and implementation.European CommissionAgencia Estatal de InvestigaciónMinisterio de Ciencia e Innovació

"Validity of a scale of Latin American perception of fear and concern transmitted by the media during the pandemic (MED-LAT-COVID-19)"

"Introduction: The pandemic has caused fear, especially due to the daily disseminated news; however, there is not an instrument to measure this fear in multiple realities. Objective: To validate a scale for Latin American perception of fear and concern transmitted by the media during the pandemic. Methodology: This is an instrumental study. The survey was based on an instrument which was pre-validated in Peru and submitted to 15 experts in almost 10 countries. Subsequently, thousands of people were surveyed in 13 Latin American countries, whose answers were used for descriptive statistics for validation. Results: Confirmatory Factor Analysis (CFA) generated two re-specifications, where four items were eliminated from the original scale. With these changes, the global goodness of fit (absolute and incremental) were satisfactory (CFI ¼ 0.978; TLI ¼ 0.964; GFI ¼ 0.976; AGFI ¼ 0.949; RMSEA ¼ 0.075 and RMR ¼ 0.029). The first factor measures the media exaggeration (three questions); the second, the fear transmitted by the media (three questions); and the third, the fear transmitted by others different from the media (two questions). The Cronbach’s alpha coefficient was higher than 0.70 for the scale and its factors. Conclusion: The MED-LAT-COVID-19 scale reported a good adjustment. It has eight items in three factors, which could be measured in an isolated way, or along with other tests that assess mental health in the current pandemic context.

Relationship between cognition and age at onset of first-episode psychosis: comparative study between adolescents, young adults, and adults

Psychotic disorders typically manifest from late adolescence to early adulthood, and an earlier onset might be associated with greater symptom severity and a worse long-term prognosis. This study aimed to compare the cognitive characteristics of patients with first-episode psychosis (FEP) by their age at onset. We included 298 patients diagnosed with FEP and classified them as having an early onset (EOS), youth onset (YOS), or adult onset (AOS) based on age limits of = 25 years (N = 116), respectively. Socio-demographic and clinical variables included age at baseline, gender, socio-economic status, antipsychotic medication, DSM-IV diagnoses assessed by clinical semi-structured interview, psychotic symptom severity, and age at onset. Neuropsychological assessment included six cognitive domains: premorbid intelligence, working memory, processing speed, verbal memory, sustained attention, and executive functioning. The EOS group had lower scores than the YOS or AOS groups in global cognition, executive functioning, and sustained attention. Although the scores in the YOS group were intermediate to those in the EOS and AOS groups for most cognitive factors, no statistically significant differences were detected between the YOS and AOS groups. Age at onset results in specific patterns of cognitive interference. Of note, impairment appears to be greater with EOS samples than with either YOS or AOS samples. A longitudinal study with a larger sample size is needed to confirm our findings

Generic boundaries in subtribe Saussureinae (Compositae: Cardueae): Insights from Hyb-Seq data

The subtribe Saussureinae is a highly speciose group with more than 600 species distributed in the Northern Hemisphere and is particularly species-rich at the high mountains of central and eastern Asia. Saussurea and Jurinea are the two main genera described within the subtribe. However, up to 15 satellite genera are recognized in some recent taxonomic treatments with an analytical viewpoint. For the first time, we carried out a complete sampling to clarify generic boundaries based on a well-resolved phylogeny of Saussureinae. We employed a Hyb-Seq technique that targets 1061 nuclear conserved ortholog loci designed for Compositae. After a filtering of potential paralogs, 588 loci were retained to infer phylogenetic trees under concatenation and coalescence approaches. High branch support resolution was recovered at the generic level, but a non-monophyletic pattern was detected for most of the genera as they are currently circumscribed. Accordingly, we propose a new generic delimitation based on the three main clades recovered in the backbone tree, which are also in agreement with morphological evidence: Dolomiaea, Saussurea, and Jurinea. Following this classification into three genera, 18 new combinations are proposed. This new genus delineation will be used as a basis for future evolutionary studies in the Saussureinae.Financial support from the Ministerio de Ciencia e Innovación (Project CGL2015-66703-P MINECO/FEDER, UE and Ph.D. grant to Sonia Herrando-Moraira) and the Catalan government (“Ajuts a grups consolidats” 2017-SGR1116) is also greatly acknowledged. This study has been performed under the Ph.D. program “Plant Biology and Biotechnology” of the Autonomous University of Barcelona (UAB)INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION TAXONOMIC IMPLICATIONS NOTE ADDED IN PROOF AUTHOR CONTRIBUTIONS ACKNOWLEDGMENT