Tandem Solar Cell Concept Using Black Silicon for Enhanced Infrared Absorption

AbstractIn this work we present a novel tandem solar cell concept that is based on enhanced below band gap infrared absorption. The solar cell structure is based on silicon and infrared activated Black Silicon. Infrared active Black Silicon is produced by exposing silicon to fs-laser pulses. It features an enhanced IR absorption, when processed under a sulfur-containing atmosphere. Then sulfur is incorporated into the silicon lattice during laser processing providing energy states in the band gap. This silicon based tandem cell thus absorbs light with wavelengths beyond 1.1μm. This can potentially increase the overall efficiency. In this paper we present the first experimental realization of this concept. We use a standard aluminium-back-surface-field (Al-BSF) silicon solar cell and implement a Black Silicon solar cell on its rear side for enhanced IR absorption. Current and voltage measurements show the feasibility of our concept

Tailoring the Absorption Properties of Black Silicon

AbstractSamples of crystalline silicon for use as solar cell material are structured and hyperdoped with sulfur by irradiation with femtosecond laser pulses under a sulfur hexafluoride atmosphere. The sulfur creates energy levels in the silicon band gap, allowing light absorption in the infrared wavelength regime, which offers the potential of a significant efficiency increase. This Black Silicon is a potential candidate for impurity or intermediate band photovoltaics. In this paper we determine the laser processed sulfur energy levels by deep-level transient spectroscopy (DLTS). We present how the number of laser pulses per sample spot influence the sulfur energy levels and hence the DLTS spectra. Further we show that changing the laser pulse by splitting it with a Michelson interferometer setup results in altered absorption which is most likely due to altered sulfur energy levels. This contribution focuses on the possibility of controlling the sulfur in Black Silicon through manipulating the laser pulse shape. As a first step samples of microstructured silicon are fabricated with doubled laser pulses at two different laser pulse distances and the absorption spectra by integrating sphere measurements are compared

Providing the Context for Intentional Learning

This article is written in response to Sharon Derry's article “Remediating Academic Difficulties Through Strategy Training: The Acquisition of Useful Knowledge.” The features of effective strategy instruction, to which Derry refers, are illustrated by examining the nature of the decisions the teacher confronts; specifically, determining the purposes of instruction, the context in which instruction occurs, and the roles of the teacher and students in instruction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69150/2/10.1177_074193259001100608.pd

Dielectric material options for integrated capacitors

Future MIM capacitor generations will require significantly increased specific capacitances by utilization of high-k dielectric materials. In order to achieve high capacitance per chip area, these dielectrics have to be deposited in three-dimensional capacitor structures by ALD or AVD (atomic vapor deposition) process techniques. In this study eight dielectric materials, which can be deposited by these techniques and exhibit the potential to reach k-values of over 50 were identified, prepared and characterized as single films and stacked film systems. To primarily focus on a material comparison, preliminary processes were used for film deposition on planar test devices. Measuring leakage current density versus the dielectric constant k shows that at low voltages (=1 V) dielectrics with k-values up to 100 satisfy the typical leakage current density specification o

Examining the Context of Strategy Instruction

The goal of literacy instruction is to teach reading and writing as tools to facilitate thinking and reasoning in a broad array of literacy events. An important difference in the disposition of children to participate in literacy experiences is the extent to which they engage in intentional self-regulated learning. The contexts attending six traditional models of strategy instruction are examined. An exploratory study, conducted with heterogeneous third graders, is reported, examining the implementation and outcomes of three models of strategy instruction—Direct Instruction, Reciprocal Teaching, and Collaborative Problem Solving—which manipulated teacher and student control of activity, as well as the instructional context.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69008/2/10.1177_074193259101200306.pd

E.U. paediatric MOG consortium consensus: Part 5 – Treatment of paediatric myelin oligodendrocyte glycoprotein antibody-associated disorders

In recent years, the understanding about the different clinical phenotypes, diagnostic and prognostic factors of myelin oligodendrocyte glycoprotein-antibody-associated disorders (MOGAD) has significantly increased. However, there is still lack of evidence-based treatment protocols for acute attacks and children with a relapsing course of the disease. Currently used acute and maintenance treatment regimens are derived from other demyelinating central nervous system diseases and are mostly centrespecific. Therefore, this part of the Paediatric European Collaborative Consensus attempts to provide recommendations for acute and maintenance therapy based on clinical experience and evidence available from mainly retrospective studies. In the acute attack, intravenous methy

Mapping subnational HIV mortality in six Latin American countries with incomplete vital registration systems

BackgroundHuman immunodeficiency virus (HIV) remains a public health priority in Latin America. While the burden of HIV is historically concentrated in urban areas and high-risk groups, subnational estimates that cover multiple countries and years are missing. This paucity is partially due to incomplete vital registration (VR) systems and statistical challenges related to estimating mortality rates in areas with low numbers of HIV deaths. In this analysis, we address this gap and provide novel estimates of the HIV mortality rate and the number of HIV deaths by age group, sex, and municipality in Brazil, Colombia, Costa Rica, Ecuador, Guatemala, and Mexico.MethodsWe performed an ecological study using VR data ranging from 2000 to 2017, dependent on individual country data availability. We modeled HIV mortality using a Bayesian spatially explicit mixed-effects regression model that incorporates prior information on VR completeness. We calibrated our results to the Global Burden of Disease Study 2017.ResultsAll countries displayed over a 40-fold difference in HIV mortality between municipalities with the highest and lowest age-standardized HIV mortality rate in the last year of study for men, and over a 20-fold difference for women. Despite decreases in national HIV mortality in all countries-apart from Ecuador-across the period of study, we found broad variation in relative changes in HIV mortality at the municipality level and increasing relative inequality over time in all countries. In all six countries included in this analysis, 50% or more HIV deaths were concentrated in fewer than 10% of municipalities in the latest year of study. In addition, national age patterns reflected shifts in mortality to older age groups-the median age group among decedents ranged from 30 to 45years of age at the municipality level in Brazil, Colombia, and Mexico in 2017.ConclusionsOur subnational estimates of HIV mortality revealed significant spatial variation and diverging local trends in HIV mortality over time and by age. This analysis provides a framework for incorporating data and uncertainty from incomplete VR systems and can help guide more geographically precise public health intervention to support HIV-related care and reduce HIV-related deaths.Peer reviewe

Mapping subnational HIV mortality in six Latin American countries with incomplete vital registration systems

Background: Human immunodeficiency virus (HIV) remains a public health priority in Latin America. While the burden of HIV is historically concentrated in urban areas and high-risk groups, subnational estimates that cover multiple countries and years are missing. This paucity is partially due to incomplete vital registration (VR) systems and statistical challenges related to estimating mortality rates in areas with low numbers of HIV deaths. In this analysis, we address this gap and provide novel estimates of the HIV mortality rate and the number of HIV deaths by age group, sex, and municipality in Brazil, Colombia, Costa Rica, Ecuador, Guatemala, and Mexico. Methods: We performed an ecological study using VR data ranging from 2000 to 2017, dependent on individual country data availability. We modeled HIV mortality using a Bayesian spatially explicit mixed-effects regression model that incorporates prior information on VR completeness. We calibrated our results to the Global Burden of Disease Study 2017. Results: All countries displayed over a 40-fold difference in HIV mortality between municipalities with the highest and lowest age-standardized HIV mortality rate in the last year of study for men, and over a 20-fold difference for women. Despite decreases in national HIV mortality in all countries�apart from Ecuador�across the period of study, we found broad variation in relative changes in HIV mortality at the municipality level and increasing relative inequality over time in all countries. In all six countries included in this analysis, 50 or more HIV deaths were concentrated in fewer than 10 of municipalities in the latest year of study. In addition, national age patterns reflected shifts in mortality to older age groups�the median age group among decedents ranged from 30 to 45 years of age at the municipality level in Brazil, Colombia, and Mexico in 2017. Conclusions: Our subnational estimates of HIV mortality revealed significant spatial variation and diverging local trends in HIV mortality over time and by age. This analysis provides a framework for incorporating data and uncertainty from incomplete VR systems and can help guide more geographically precise public health intervention to support HIV-related care and reduce HIV-related deaths

Art and the toxic politics of waste: Latin America. a roundtable discussion with filmmakers and researchers at University College London

Between December 2020 and January 2021, Hanna Baumann and I organized a twofold event around the topic of waste in contemporary cities. Back then, she was analyzing a series of artistic representations of Lebanon’s environmental crises in relation to political and spatial toxicity, and I was starting a project of ecological history at the neighborhood scale (specifically in London and Leicester), looking into how the proximity of sewage waste had been experienced by local residents across long timespans. She and I talked about the intersections of these concerns, and started asking ourselves a series of questions about the deeply grounded, yet also deeply elusive quality of these processes that seemed to transcend geographies. Experiences of toxicity are riddled with uncertainty, as ethnographers like Javier Auyero and Debora Swistun discover in a Buenos Aires shantytown (Auyero and Swistun 2009). Different temporalities coexist in toxic processes, entangling human and non-human entities into extremely complex environmental and political systems. How can we trace and make sense of these linkages? More specifically, how can different forms of knowledge production—and, in particular, artistic formats—account for the (often complex) trajectories of waste, its slow and difficult-to-trace impact, and the complexity of political forces at play? When we talk about toxic politics, we are thinking about them in at least three different but interrelated ways. At their most basic, they can be seen as harmful systems: structures and networks which, by their very nature, damage the polity and humans. At the same time, these are processes where inequality is negotiated, perpetuated, and deepened, and which result in tangible harm, eroding subjectivities and affecting the wellbeing of bodies, human and non-human alike. Finally, and in relation to the former two, toxic inequality continues to be deeply entwined with political, economic and symbolic interests which displace harm onto some subjectivities and bodies more than others. With these concerns in mind, we met filmmakers Marcos Prado and Martín Oesterheld to discuss two of their films, Estamira (Prado, 2005), and La multitud (Oesterheld, 2012). We were joined by researchers in culture, Geoffrey Kantaris and Gisela Heffes, and anthropologist Patrick O’Hare