In this article, we show the structural, optical, and electrical characterization of TiOx deposited by the unconventional technique of High-Pressure Sputtering (HPS). This technique has the potential to reduce the plasma-induced damage of the samples. To fabricate the TiOx, a 2-step process was used. Firstly, a thin Ti film was deposited in an Ar atmosphere. Secondly, O-2 was introduced into the HPS chamber to create an Ar/O-2 plasma that, along with low temperatures (150 degrees C or 200 degrees C), induces the oxidation of the deposited Ti film. With this approach, the Ti film is expected to behave as a capping layer that will reduce the oxidation of the Si substrate. This study aims to obtain a TiOx layer with low specific contact resistivity (rho(c)) and high minority carrier lifetime. These are crucial characteristics for obtaining high-quality selective contact. It was found that the 2-step process can oxidize the Ti layer. These HPS TiOx layers show a resistivity in the order of 0.3-10 Omega cm and a ratio Ti/O of similar to 1.9. Moreover, the SiOx regrowth is minimal since this is comparable to the native oxide. This was confirmed by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The samples fabricated with a Ti layer (similar to 4 nm) plus an oxidation temperature of 200 degrees C (duration of less than 2 h) show a low rho(c) of 0.02 Omega cm(2), an excellent transmittance (>87 %) in the visible region and an optical bandgap of 2.8 eV. These TiOx layers are amorphous, although some anatase phase crystalline clusters appear for the 200 degrees C processes. However, the minority carrier lifetime results of Si passivated by TiOx were inadequate for fabricating efficient solar cells. We also found that using the RCA oxide improved lifetime. This indicates that introducing alternative low-temperature passivating layers can solve this issue.

The electrical characteristics of solar cells are significantly influenced by the metallization process, making it a crucial step. Screen printing is the standard metallization technique, but there is an increasing interest in the development of methods that allow more versatility, higher process control, and a more efficient use of the expensive metallic pastes used. We focus here on the comparison between the standard screen-printing method, and Light-Induced Forward-Transfer (LIFT), a non-contact, very precise technique, able to transfer volumes down to picolitres. The high flexibility, using free-form designs that do not depend on any mask or physical support, and the efficient use of the metallic paste with almost no waste, are other characteristics that point out LIFT as a very promising alternative. In this paper we include the electric characterization of contacts, and solar silicon heterojunction (SHJ) cells metalized with both techniques. The results show a slightly better efficiency for the screen-printed cells, but good series resistance and fill factor values imply that LIFT is a promising alternative for device metallization.

We have deposited thin films of MoO x using high-pressure sputtering (HPS) and Ar/O 2 /H 2 atmospheres aiming at the compositional and interface control. We found that H2 impacts plasma composition, which in turn produces a reduction of the oxygen content and a change in the refractive index of the films. However, the presence of hydrogen in the plasma atmosphere enhances interfacial SiO x regrowth, as FTIR shows. TEM measurements show that this regrowth is not critical for thin films. Also, increasing the hydrogen ratio produces a change from amorphous to an amorphous/polycrystalline mixture. Lifetime measurements show that these films are adequate for their integration into test HIT -like structures, but require more work to produce competitive iVoc values.

This article studies the physical and electrical behavior of indium tin oxide layers (ITO) grown by an unconventional technique: High Pressure Sputtering (HPS), from a ceramic ITO target in a pure Ar atmosphere. This technique has the potential to reduce plasma induced damage to the samples. The aim is to obtain, at low temperature via HPS, good quality transparent conductive oxide layers for experimental photovoltaic cells with emerging selective contacts such as transition metal oxides, alkaline metal fluorides, etc. We found that the resistivity of the films was strongly dependent on Ar pressure. To obtain device-quality resistivity without intentional heating during deposition a pressure higher than 1.0 mbar was needed. These films deposited on glass were amorphous, presented a high electron mobility (up to 45 cm2V- 1s- 1) and a high carrier density (2.9 x 1020 cm-3 for the sample with the highest mobility). The optimum Ar pressure range was found at 1.5-2.3 mbar. However, the resistivity degraded with a moderate annealing temperature in air. Finally, the feasibility of the integration with photovoltaic cells was assessed by depositing on Si substrates passivated by a-Si:H. The film deposited at 1.5 mbar was uniform and amorphous, and the carrier lifetime obtained was 1.22 ms with an implied open circuit voltage of 719 mV after a 215 degrees C air anneal. The antireflective properties of HPS ITO were also demonstrated. These results show that ITO deposited by HPS is adequate for the research of solar cells with emerging selective contacts.

This work presents the implementation of ultrathin TiO2 films, deposited at room temperature by radio-frequency magnetron sputtering, as electron-selective contacts in silicon heterojunction solar cells. The effect of the working pressure on the properties of the TiO2 layers and its subsequent impact on the main parameters of the device are studied. The material characterization revealed an amorphous structure regardless of the working pressure; a rougher surface; and a blue shift in bandgap in the TiO2 layer deposited at the highest-pressure value of 0.89 Pa. When incorporated as part of the passivated full-area electron contact in silicon heterojunction solar cell, the chemical passivation provided by the intrinsic a-Si:H rapidly deteriorates upon the sputtering of the ultra-thin TiO2 films, although a short anneal is shown to restore much of the passivation lost. The deposition pressure and film thicknesses proved to be critical for the efficiency of the devices. The film thicknesses below 2 nm are necessary to reach open-circuit values above 660 mV, regardless of the deposition pressure. More so, the fill-factor showed a strong dependence on deposition pressure, with the best values obtained for the highest deposition pressure, which we correlated to the porosity of the films. Overall, these results show the potential to fabricate silicon solar cells with a simple implementation of electron-selective TiO2 contact deposited by magnetron sputtering. These results show the potential to fabricate silicon solar cells with a simple implementation of electron-selective TiO2 contact.

The silicon heterojunction solar cell (SHJ) is considered the dominant state-of-the-art silicon solar cell technology due to its excellent passivation quality and high efficiency. However, SHJ’s light management performance is limited by its narrow optical absorption in long-wave near-infrared (NIR) due to the front, and back tin-doped indium oxide (ITO) layer’s free carrier absorption and reflection losses. Despite the light-trapping efficiency (LTE) schemes adopted by SHJ in terms of back surface texturing, the previous investigations highlighted the ITO layer as a reason for an essential long-wavelength light loss mechanism in SHJ solar cells. In this study, we propose the use of Molybdenum disulfide (MoS2) as a way of improving back-reflection in SHJ. The text presents simulations of the optical response in the backside of the SHJ applying the Monte-Carlo raytracing method with a web-based Sunsolve high-precision raytracing tool. The solar cells’ electrical parameters were also resolved using the standard electrical equivalent circuit model provided by Sunsolve. The proposed structure geometry slightly improved the SHJ cell optical current density by ~0.37% (rel.), and hence efficiency (η) by about 0.4% (rel.). The SHJ cell efficiency improved by 21.68% after applying thinner back ITO of about 30 nm overlayed on ~1 nm MoS2. The efficiency improvement following the application of MoS2 is tentatively attributed to the increased NIR absorption in the silicon bulk due to the light constructive interface with the backside components, namely silver (Ag) and ITO. Study outcomes showed that improved SHJ efficiency could be further optimized by addressing front cell components, mainly front ITO and MoS2 contact engineering.

In this work we have successfully hyperdoped germanium with tellurium with a concentration peak of 10(21) cm(-3). The resulting hyperdoped layers show good crystallinity and sub-bandgap absorption at room temperature which makes the material a good candidate for a new era of complementary metal-oxide-semiconductor-compatible short-wavelength-infrared photodetectors. We obtained absorption coefficients ci higher than 4.1 x 10(3) cm(-1) at least up to 3 mu m. In this study we report the temperature-dependency electrical properties of the hyperdoped layer measured in van der Pauw configuration. The electrical behaviour of this hyperdoped material can be explained with an electrical bilayer coupling/decoupling model and the values for the isolated hyperdoped layer are a resistivity of 4.25 x 10(-3) Omega.cm with an electron-mobility around -100 cm(2) V-1 s(-1).

Laser-based surface texturing treatments have been investigated as a promising option for innovative low-cost concepts to improve the light absorption of silicon heterojunction solar cells manufactured from unconventional silicon wafers. A great advantage of using a laser as a processing tool is its high precision, which lead to selected and well-controlled morphologies. This is a particularly interesting feature for multicrystalline silicon wafers, where the large number of grain boundaries makes it difficult to obtain high light-trapping morphologies by other methods. The investigations described in this work include testing different patterns on the wafer surface in order to define the best morphology to improve the light absorption. A significant decrease in reflectance (R<;9%) has been achieved by direct-laser texturization and has been compared with acid-chemical etching with average reflectance above 20%. This result suggests the enormous potential of direct laser texturization for this type of wafers, without chemical residues and its easy incorporation to the manufacturing of low-cost silicon heterojunction solar cells.

The roadmap for the development of silicon solar cells requires the introduction of passivating contacts to obtain higher efficiencies as well as to reduce the cost of production to be industrially implemented. In this context, Laser Fired Contact (LFC) on p-type silicon wafers have been shown to be an effective technique to improve efficiencies, due to their ability to reduce recombination losses on the back surface of crystalline silicon solar cells. These studies have mainly focused on high quality monocrystalline silicon wafers and there are not enough developments made with multicrystalline silicon (mc-Si) wafers. Therefore, in this work, we present the optimization of the LFC process on p-type mc-Si and its application to two types of silicon devices: diffusion and heterojunction solar cells. These rear contacts have led to improved efficiencies for both types of solar cells over similar devices with thermalized aluminum rear contacts and without back passivation. These results illustrate the enormous potential of these localized laser-contacts created for mc-Si solar cells, perfectly compatible with a lower cost industrial production.

BackgroundChagas disease (CD) is a chronic parasitic disease caused by Trypanosoma cruzi and is endemic to continental Latin America. In Spain, the main transmission route is congenital. We aimed to assess adherence to regional recommendations of universal screening for CD during pregnancy in Latin American women in the province of Alicante from 2014 to 2018.Methodology/principal findingsRetrospective quality study using two data sources: 1) delivery records of Latin American women that gave birth in the 10 public hospitals of Alicante between January 2014 and December 2018; and 2) records of Chagas serologies carried out in those centers between May 2013 and December 2018. There were 3026 deliveries in Latin American women during the study period; 1178 (38.9%) underwent CD serology. Screening adherence ranged from 17.2% to 59.3% in the different health departments and was higher in Bolivian women (48.3%). Twenty-six deliveries (2.2%) had a positive screening; CD was confirmed in 23 (2%) deliveries of 21 women. Bolivians had the highest seroprevalence (21/112; 18.7%), followed by Colombians (1/333; 0.3%) and Ecuadorians (1/348; 0.3%). Of 21 CD-positive women (19 Bolivians, 1 Colombian, 1 Ecuadorian), infection was already known in 12 (57.1%), and 9 (42.9%) had already been treated. Only 1 of the 12 untreated women (8.3%) was treated postpartum. Follow-up started in 20 of the 23 (87.0%) neonates but was completed only in 11 (47.8%); no cases of congenital transmission were detected. Among the 1848 unscreened deliveries, we estimate 43 undiagnosed cases of CD and 1 to 2 undetected cases of congenital transmission.Conclusions/significanceAdherence to recommendations of systematic screening for CD in Latin American pregnant women in Alicante can be improved. Strategies to strengthen treatment of postpartum women and monitoring of exposed newborns are needed. Currently, there may be undetected cases of congenital transmission in our province.

In this work we have explored the growth by high pressure sputtering (HPS) of materials intended for novel selective contacts for photovoltaic cells. This technique shows promise for the low-damage low-temperature deposition of PV materials. We studied the deposition of ITO, MoOx and TiOx using pure Ar and mixed Ar/O-2 atmospheres as well as ceramic or metallic targets. We show that HPS deposition of these materials is feasible. The growth rate is greatly reduced when oxygen is added to the argon sputtering atmosphere. The best sputtering RF power was 20-45 W for the pressure range studied. Finally, as-deposited films present high surface recombination, but a mild hot plate anneal at 200 degrees C recovers long effective lifetimes.

Transparent conductive electrodes based on graphene have been previously proposed as an attractive candidate for optoelectronic devices. While graphene alone lacks the antireflectance properties needed in many applications, it can still be coupled with traditional transparent conductive oxides, further enhancing their electrical performance. In this work, the effect of combining indium tin oxide with between one and three graphene monolayers as the top electrode in silicon heterojunction solar cells is analyzed. Prior to the metal grid deposition, the electrical conductance of the hybrid electrodes was evaluated through reflection-mode terahertz time-domain spectroscopy. The obtained conductance maps showed a clear electrical improvement with each additional graphene sheet. In the electrical characterization of the finished solar cells, this translated to a meaningful reduction in the series resistance and an increase in the devices' fill factor. On the other hand, each additional sheet absorbs part of the incoming radiation, causing the short circuit current to simultaneously decrease. Consequently, additional graphene monolayers past the first one did not further enhance the efficiency of the reference cells. Ultimately, the increase obtained in the fill factor endorses graphene-based hybrid electrodes as a potential concept for improving solar cells' efficiency in future novel designs.

Las habilidades de comunicación constituyen una competencia fundamental en profesionales de la salud. Educarlas fomenta el profesionalismo en estudiantes y graduados. El objetivo del presente trabajo es describir un curso diseñado para optimizar la comunicación con pacientes y colegas en estudiantes de sexto año de medicina que han recibido formación en comunicación desde primer año. Es un curso optativo de 5 semanas que se realiza parcialmente online, con sesiones presenciales semanales y una evaluación final. Como metodología para el aprendizaje y evaluación se utiliza la técnica de role play y se desarrolla un feedback grupal: del alumno involucrado, pares y docentes. En esta primera entrega se describe el curso, los temas troncales y la metodología de role play utilizada, además de una breve encuesta realizada al concluir. Se incluyen las condiciones fundamentales para dar feedback. Como conclusión inicial, este curso aportaría a la formación integral de los estudiantes, al jerarquizar habilidades indispensables. Tanto el role play como el feedback grupal son altamente valorados por estudiantes y docentes.

Una perforacion es una comunicacion entre el conducto radicular y el tejido de soporte dental. Esta puede ocurrir debido a la reabsorcion del tejido duro dental, caries o por terapia endodontica.1 La perforacion del piso de la camara pulpar es una complicacion que puede producirse durante la preparacion del acceso o en la instrumentacion del conducto radicular, causando falla endodoncia. El tratamiento puede ser con o sin cirugia y el pronostico generalmente es excelente si el problema se diagnostica y repara correctamente. Biodentine es un material a base de silicato de calcio de alta pureza compuesto de silicato tricalcico, carbonato de calcio, oxido de circonio y un liquido que contiene cloruro de calcio como acelerador de fraguado y agente reductor de agua. Se recomienda como sustituto de dentina bajo restauraciones de resina compuesta y como material de reparacion endodontica debido a su buena capacidad de sellado, alta resistencia a la resistencia a la compresion, tiempo de fraguado corto, biocompatibilidad, bioactividad y propiedades de biomineralizacion.

ZnO:Al films of about 400 nm thick were deposited on glass substrates by a magnetron sputtering system. We used a diode-pumped solid-state laser (Nd:YVO4) working at 355 nm to texture the AZO films. The texture patterns used were: a simple pattern obtained by scribing parallel grooves with a constant spacing, and a crisscross pattern obtained with a second array of parallel laser scribes perpendicular to the first one. Varying the process parameters we obtained different morphologies, with scribes ranging from widely spaced to overlapping grooves, and from almost undamaged surfaces to scribes that reached the glass substrate. The light scattering produced by the textured ZnO:Al films was evaluated through the haze factor.

With the objective of increasing light scattering and obtaining a higher light absorption in thin-film solar cells, we have textured aluminum-doped zinc oxide (ZnO:Al) films deposited by RF magnetron sputtering on glass substrates using a nanosecond pulsed laser working at 355 nm. The textures have been achieved by simply patterning the ZnO:Al surfaces through direct scribing, using either a linear pattern consisting of equally separated parallel grooves, or a crisscross pattern obtained by performing a second array of laser scribes perpendicular to the former. The relationship between the light scattering properties of the textured films and its morphology are discussed considering two different scattering sources:the pattern formed by the grooves that works as a diffraction grating, and a random roughness of low amplitude created during the laser process. To further characterize the textured samples, amorphous silicon solar cells were deposited onto ZnO:Al films with different textures and their spectral response and short-circuit current (J(sc)) measured. An increment of 15% in J(sc) compared to non-textured solar cells is achieved, with ample room for improvement.

La ciencia para la sustentabilidad plantea incluir en investigaciones y acciones los conocimientos y técnicas desarrollados por diversos sectoresde la sociedad. Esta propuesta reconoce que la complejidad de los problemas ambientales rebasa los enfoques y ritmos de la investigacióncientífica predominante y brinda la posibilidad de acortar tiempos para la acción, aprovechando integralmente la experiencia humana. Presentamosun panorama de nuestro trabajo en: 1) investigación participativa, 2) procesos educativos para la participación y 3) procesos institucionalesde comunicación y participación. Se abordan estudios socioecológicos participativos que involucran innovación tecnológica e intercambios deexperiencias técnicas y organizativas para atender problemas ambientales en el valle de Tehuacán, la sierra Tarahumara, la montaña de Guerrero y la costa sur de Jalisco, poniendo énfasis en la construcción de alternativas. Se muestra la experiencia de prácticas de investigación de alumnos de posgrado y de la licenciatura en Ciencias Ambientales, UNAM. Ambos programas abordan problemas concretos en comunidades rurales en colaboración con organizaciones civiles y sociales, y comunidades. Se resumen las propuestas de vinculación institucional del Instituto de Investigaciones en Ecosistemas y Sustentabilidad (IIES) para atender problemas ambientales con manejadores de ecosistemas y tomadores de decisiones. Se discute la importancia de fortalecer procesos participativos como base para impulsar la colaboración académica en la construcción de perspectivas socioecológicas sustentables.

Many semiconductor technologies require the patterning of films to create features not easily achieved during growth or deposition. In the case of transparent conductive oxides (TCOs), this is typically realized through direct laser-scribing. Although there are models conceived to predict the depth of a scribe, the necessary parameters to obtain a given depth are usually found by trial and error. This is mostly due to the models usually being highly elaborated and dependent on difficult to measure variables. In this paper we introduce a method for predicting the ablation depth in direct laser-scribing processes based on laser-processing parameters and convenient properties like the ablation threshold fluence and the laser penetration depth. In order to apply this method though, the materials must comply with two conditions: a) the material does not develop incubation with successive pulses and b) the ablation depth obtained at any position by a single pulse is determined by the fluence reaching that point. We present experimental data using nanosecond sources and a wavelength of 355 nm for TCOs Indium doped Tin Oxide and Aluminum doped Zinc Oxide that endorse the proposed method as a tool for predicting the ablated depth in laser scribes. (C) 2017 Published by Elsevier B.V.

Light trapping strategies that lead to an enhancement of the light absorbed by a device is a direct way to improve solar cells behavior. Light trapping strategies that lead to an enhancement of the light absorbed by a device is a direct way to improve solar cells behavior. The texturization of one or more surfaces is an industry standard in solar cells manufacturing. In the particular case of crystalline- and multi-crystalline-silicon wafers, this is usually achieved by means of a chemical etching. The control of the final morphology is limited though, especially in multi-crystalline silicon wafers where the etching rate in basic solutions is dependent on the crystal orientation of the silicon grains. The use of laser sources has opened the door to new texturing techniques leading to different kind of morphologies. An example is the use of laser pulses together with chemical etching or the texturization by direct laser scribing [1, 2]. In this work, we study the changes in the incident light reflection of silicon samples when they are textured by direct laser beams and compare them with similar samples textured by standard chemical etching and optimized for its use in silicon heterojunction solar cells.