PEI based selective contact for different photovoltaic absorber materials

La investigación en tecnologías fotovoltaicas se ha basado mayoritariamente en la teoría de la unión PN pero, gracias a la interpretación mediante potenciales electroquímicos más que campos eléctricos, la visión de una célula solar como un absorbedor más dos filtros ha ganado peso en los últimos años. Por este motivo, la investigación en nuevos contactos selectivos es, actualmente, de gran relevancia. Sobre todo para aquellos que no incorporan procesos a altas temperaturas, ni materiales críticos o tóxicos. En el trabajo que se presenta a continuación se ha podido constatar los beneficios de utilizar una unión "Metal-Dipolo-Semiconductor" con Polietilenimina (PEI) como contacto selectivo de electrones. Con el fin de caracterizar la calidad del contacto se han realizado diferentes medidas eléctricas y ópticas, con los resultados de las cuales se ha elaborado un modelo teórico que explica el comportamiento detrás del contacto de PEI. Además, se han fabricado diferentes células solares a partir de varios absorbedores, encontrando un contacto libre de materiales críticos y de procesos altamente costosos con el que se han obtenido resultados bastante prometedores. Actualmente, las células fotovoltaicas basadas en silicio cristalino (c-Si) dominan ampliamente el mercado gracias a sus eficiencias comerciales superiores al 15%. Pero, debido a que la mayoría de estos dispositivos utilizan interficies dopadas y contactos metálicos directamente depositados, el coste energético vinculado a su fabricación es muy elevado. Depositando fácilmente una fina capa de PEI entre el semiconductor y el metal mediante la técnica de "spin-coating", somos capaces de fabricar un contacto de gran eficiencia sin necesidad de dopar por difusión térmica la interfície del absorbedor. Además, al estudiar este contacto orgánico sobre diferentes absorbedores de capa fina, donde el uso de materiales críticos y tóxicos es uno de sus máximos inconvenientes, hemos podido presentar un contacto con unas prestaciones muy similares a las del contacto de electrones clásico de CdS, pero sin involucrar a este.La recerca en tecnologies fotovoltaiques s'ha basat majoritàriament en la teoria de la unió PN però, gràcies a la interpretació mitjançant potencials electroquímics més que camps elèctrics, la visió d'una cèl·lula solar com a un absorbidor més dos filtres ha guanyat pes en els últims anys. Per aquest motiu, la investigació en nous contactes selectius és, actualment, de gran rellevància. Sobretot per aquells que no incorporen processos a altes temperatures, ni materials crítics o tòxics. En el treball que es presenta a continuació s'ha pogut constatar els beneficis d'utilitzar una unió "Metall-Dipol-Semiconductor" amb Polietilenimina (PEI) com a contacte selectiu d'electrons. Per tal de caracteritzar la qualitat del contacte s'han realitzat diferents mesures elèctriques i òptiques, amb els resultats de les quals s'ha elaborat un model teòric explicant el comportament darrera el contacte de PEI. A més, s'han fabricat diferents cèl·lules solars a partir de diversos absorbidors, trobant un contacte lliure de materials crítics i de processos altament costosos amb el qual s'han obtingut resultats força prometedors. Actualment, les cèl·lules fotovoltaiques basades en silici cristal·lí (c-Si) dominen àmpliament el mercat gràcies a les seves eficiències comercials superiors al 15%. Però, degut a que la majoria d'aquests dispositius utilitzen interfícies dopades i contactes metàl·lics directament dipositats, el cost energètic vinculat a la seva fabricació és molt elevat. Dipositant fàcilment una fina capa de PEI entre el semiconductor i el metall mitjançant la tècnica de "spin-coating", som capaços de fabricar un contacte de gran eficiència sense necessitat de dopar per difusió tèrmica la interfície de l'absorbidor. A més, al estudiar aquest contacte orgànic sobre diferents absorbidors de capa fina, on l'ús de materials crítics i tòxics és un dels seus màxims inconvenients, hem pogut presentar un contacte amb unes prestacions molt similars a les del contacte d'electrons clàssic de CdS, però sense involucrar aquest.Research in photovoltaic (PV) devices has usually focused on PN junction theory. However, with the new perspective on electronic transport driven by electrochemical potentials rather than electrical fields, the understanding of solar cells as the combination of an absorber and two selective contacts has gained strength. As a consequence, there has been a growing interest in researching new selective contacts to obtain high efficiency and low-temperature processed photovoltaic devices that can reduce their cost and ecological footprint. In this work, we report the promising performance obtained with a "Metal-Dipolar-Semiconductor" junction based on Polyethylenimine (PEI) as electron transport layer. Electrical and optical characterization have been performed to determine the contact quality over different absorbers, and a theoretical model explaining these results has been presented. Different photovoltaic devices have been fabricated and characterized, finding promising free-dopant and CRM-free architectures for different absorbers. Currently, the global photovoltaic market is dominated by crystalline silicon (c-Si) based technologies with heavily doped, directly metallized contacts, which implies high-temperature steps. With the simple deposition of PEI between the semiconductor and the metal through spin-coating technique, we were able to obtain high-performance contacts without doping. In addition, regarding the study over thin-film absorbers, where the use of critical raw materials (CRM) is one of their main drawbacks, we proved that a stack combining a zinc oxide buffer layer and the polymeric interlayer yields outputs comparable to the classical CdS selective contact

Covid-19 analysis using the Gompertz Function

This report analyses the spread of COVID-19 in european countries, focusing especially on Italy and Spain, for which short-term predictions are made for the cumulative number of hospitalizations, ICUs, discharges and deaths. Taking into account the different magnitudes considered, for 1 day predictions the mean probability of a right guess is of 0.99, 0.94 for 2 day predictions, 0.89 for 3 day predictions and 0.83 for 4 day predictions2019/202

Wildland–urban interface fires in spain: summary of the policy framework and recommendations for improvement

Southern Europe is recurrently being hit by forest fires affecting wildland–urban interface (WUI) areas which, particularly in the last decade, have resulted in tremendous consequences. In the years to come, self-protection of communities will be a first priority over fire suppression, demanding better fire-resistant and resilient WUI scenarios through actions grounded on solid and sound regulations and legislation. As of today, the European Union as a whole, and the Member States in particular, are belatedly articulating new and appropriate regulations and implementing policies for the protection of WUI areas against forest fires. Spain is one of the EU Member States, holding 1.1 million ha of WUI areas (above 4% of the total forested land) and experiencing an average of 12,500 forest fires per year over the past decade. In this paper a review of the state of the art on regulations, codes, plans and recommendations on WUI fire prevention and management in Spain is presented. Shortcomings due to the current lack of building and urban planning standards and technical codes for WUI communities are highlighted. We underline some paramount needs to be covered by scientific research and fire engineering in particular topics. Some of them have received little attention in the literature related to European WUI fires while some others have been almost unexplored, such as planning of low-fuel fringes, design of road networks and accessibility, dimension of water supply networks, study of ignitability and combustibility of residential vegetation, role of construction methods and materials, and the wildland–industrial interface. Outcomes from research activities on such topics should lead to appropriately drive and inform the policy making processes on WUI fire prevention and management in Spain and, by extension, in other southern European countries under a similar situation.Postprint (author's final draft

Expanding the perspective of polymeric selective contacts in photovoltaic devices using branched polyethylenimine

This work studies the use of polymeric layers of polyethylenimine (PEI) as an interface modification of electron-selective contacts. A clearly enhanced electrical transport with lower contact resistance and significant surface passivation (about 3 ms) can be achieved with PEI modification. As for other conjugated polyelectrolytes, protonated groups of the polymer with their respective counter anions from the solvent create an intense dipole. In this work, part of the amine groups in PEI are protonated by ethanol that behaves as a weak Brønsted acid during the process. A comprehensive characterization including high-resolution compositional analysis confirms the formation of a dipolar interlayer. The PEI modification is able to eliminate completely Fermi-level pinning at metal/semiconductor junctions and shifts the work function of the metallic electrode by more than 1 eV. Induced charge transport between the metal and the semiconductor allows the formation of an electron accumulation region. Consequently, electron-selective contacts are clearly improved with a significant reduction of the specific contact resistance (less than 100 mO·cm2). Proof-of-concept dopant-free solar cells on silicon were fabricated to demonstrate the beneficial effect of PEI dipolar interlayers. Full dopant-free solar cells with conversion efficiencies of about 14% could be fabricated on flat wafers. The PEI modification also improved the performance of classical high-efficiency heterojunction solar cells.This research has been supported by the Spanish government through Grants PID2019-109215RB-C41, PID2019109215RB-C43, PID2020-115719RB-C21, and PID2020116719RB-C41 and funded by MCIN/AEI/10.13039/ 501100011033. Besides this the authors would like to thank Prof. Jordi LLorca for his expertise and helpful discussions of XPS results, as well as Dr. Rodrigo Fernández-Pacheco of the Laboratorio de Microscopias Avanzadas (LMA-INA) of Zaragoza for the HRTEM images and EDS and EELS analysis, and Guillaume Sauthier from ICN2 for his contribution through UPS measurements and discussions.Peer ReviewedPostprint (published version

Consens d’escales i eines per a la valoració multidimensional de les persones a Catalunya

Model d'atenció integral; Valoració multidimensional; DiagnòsticModelo de atención integral; Valoración multidimensional; DiagnósticoComprehensive care model; Multidimensional valuation; DiagnosisActualment no existeix a Catalunya un consens sobre quin hauria de ser el mínim comú denominador d’escales i eines d’elecció per a la valoració de les diferents dimensions de les persones grans amb multimorbiditat, fragilitat, cronicitat complexa o avançada. Aquest escenari fa evident la necessitat de disposar d’escales i eines consensuades i compartides que facilitin l’aproximació multidimensional a aquestes persones de forma objectiva i pragmàtica, amb l’objectiu d'ajudar els professionals en aquest procés d’individualització de l’atenció. És per aquest motiu que, impulsat per la Direcció General de Planificació i Recerca en Salut i per l’oficina eSalut, s’ha promogut i desenvolupat aquest consens i es vol assegurar que la proposta pugui ser suportada en l’entorn digital

Role of age and comorbidities in mortality of patients with infective endocarditis

[Purpose]: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. [Methods]: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015.Patients were stratified into three age groups:<65 years,65 to 80 years,and ≥ 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. [Results]: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 ≥ 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients ≥80 years who underwent surgery were significantly lower compared with other age groups (14.3%,65 years; 20.5%,65-79 years; 31.3%,≥80 years). In-hospital mortality was lower in the <65-year group (20.3%,<65 years;30.1%,65-79 years;34.7%,≥80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%,≥80 years; p = 0.003).Independent predictors of mortality were age ≥ 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI ≥ 3 (HR:1.62; 95% CI:1.39–1.88),and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared,the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. [Conclusion]: There were no differences in the clinical presentation of IE between the groups. Age ≥ 80 years, high comorbidity (measured by CCI),and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

Fluid challenges in intensive care: the FENICE study A global inception cohort study

Fluid challenges (FCs) are one of the most commonly used therapies in critically ill patients and represent the cornerstone of hemodynamic management in intensive care units. There are clear benefits and harms from fluid therapy. Limited data on the indication, type, amount and rate of an FC in critically ill patients exist in the literature. The primary aim was to evaluate how physicians conduct FCs in terms of type, volume, and rate of given fluid; the secondary aim was to evaluate variables used to trigger an FC and to compare the proportion of patients receiving further fluid administration based on the response to the FC.This was an observational study conducted in ICUs around the world. Each participating unit entered a maximum of 20 patients with one FC.2213 patients were enrolled and analyzed in the study. The median [interquartile range] amount of fluid given during an FC was 500 ml (500-1000). The median time was 24 min (40-60 min), and the median rate of FC was 1000 [500-1333] ml/h. The main indication for FC was hypotension in 1211 (59 %, CI 57-61 %). In 43 % (CI 41-45 %) of the cases no hemodynamic variable was used. Static markers of preload were used in 785 of 2213 cases (36 %, CI 34-37 %). Dynamic indices of preload responsiveness were used in 483 of 2213 cases (22 %, CI 20-24 %). No safety variable for the FC was used in 72 % (CI 70-74 %) of the cases. There was no statistically significant difference in the proportion of patients who received further fluids after the FC between those with a positive, with an uncertain or with a negatively judged response.The current practice and evaluation of FC in critically ill patients are highly variable. Prediction of fluid responsiveness is not used routinely, safety limits are rarely used, and information from previous failed FCs is not always taken into account

TFG 2015/2016

Amb aquesta publicació, EINA, Centre universitari de Disseny i Art adscrit a la Universitat Autònoma de Barcelona, dóna a conèixer el recull dels Treballs de Fi de Grau presentats durant el curs 2015-2016. Voldríem que un recull com aquest donés una idea més precisa de la tasca que es realitza a EINA per tal de formar nous dissenyadors amb capacitat de respondre professionalment i intel·lectualment a les necessitats i exigències de la nostra societat. El treball formatiu s’orienta a oferir resultats que responguin tant a paràmetres de rigor acadèmic i capacitat d’anàlisi del context com a l’experimentació i la creació de nous llenguatges, tot fomentant el potencial innovador del disseny.Con esta publicación, EINA, Centro universitario de diseño y arte adscrito a la Universidad Autónoma de Barcelona, da a conocer la recopilación de los Trabajos de Fin de Grado presentados durante el curso 2015-2016. Querríamos que una recopilación como ésta diera una idea más precisa del trabajo que se realiza en EINA para formar nuevos diseñadores con capacidad de responder profesional e intelectualmente a las necesidades y exigencias de nuestra sociedad. El trabajo formativo se orienta a ofrecer resultados que respondan tanto a parámetros de rigor académico y capacidad de análisis, como a la experimentación y la creación de nuevos lenguajes, al tiempo que se fomenta el potencial innovador del diseño.With this publication, EINA, University School of Design and Art, affiliated to the Autonomous University of Barcelona, brings to the public eye the Final Degree Projects presented during the 2015-2016 academic year. Our hope is that this volume might offer a more precise idea of the task performed by EINA in training new designers, able to speak both professionally and intellectually to the needs and demands of our society. The educational task is oriented towards results that might respond to the parameters of academic rigour and the capacity for contextual analysis, as well as to considerations of experimentation and the creation of new languages, all the while reinforcing design’s innovative potential

Covid-19 analysis using the Gompertz Function

This report analyses the spread of COVID-19 in european countries, focusing especially on Italy and Spain, for which short-term predictions are made for the cumulative number of hospitalizations, ICUs, discharges and deaths. Taking into account the different magnitudes considered, for 1 day predictions the mean probability of a right guess is of 0.99, 0.94 for 2 day predictions, 0.89 for 3 day predictions and 0.83 for 4 day predictions2019/202