Interdigitated back-contacted(IBC) c-Si solar cells based on laser processed dielectric layers

The goal of this thesis is the fabrication of high-efficiency interdigitated back-contact (IBC) c-Si solar cell at low temperature and low-cost manufacturing technology. This thesis proposes a new concept and at the same time a simple and elegant fabrication process that has been fully developed and culminated with the fabrication of a "cold" IBC solar cell as a proof-of-concept. To carry out this proposal, we focus our research on the study and application of low-temperature processes such as Atomic Layer Deposition (ALD) and Plasma-enhanced Chemical Vapor Deposition (PECVD) to deposit dielectric layers. A process based on laser techniques was also developed to be applied on these dielectric layers to form p+ and n+ regions into the c-Silicon sample. The laser highly-doped regions are formed in a point-like structure avoiding the classical high-temperature diffusion process. The dielectrics used, Al2O3 and a-SiCx (n) stack , play the role of aluminum and phosphorous dopant sources respectively. A detailed study has been accomplished to find the best laser parameters and obtain the optimal p++ and n++ junction. At the same time, these layers work as excellent surface passivating films and improves the front and the rear reflectance. To get the film which better fulfills these tasks, an extensive investigation has been performed to optimize the deposition and post-deposition processes in terms of temperature, time and layer thickness. In order to fabricate the "cold" IBC cell, we firstly developed a IBC cell performed on p-type FZ c-Si with a conventional phosphorous diffusion. The SiCx(n) stack passivated the n region interface as well as provided phosphorous atoms to create n++ regions or selective emitter structures after laser processing. The aluminium atoms supplied by the Al2O3 layer formed a p++ region or Back-surface field (BSF) after the laser processing and simultaneously passivated the p region interface. A promising efficiency of 18.7% (Jsc= 39.1 mA/cm2, Voc= 638 mV, FF= 75.3%) was obtained as a result of this new concept. The first "cold" IBC cell was obtained after elimination of conventional phosphorous diffusion and rearrangement of the fabrication steps in order to reduce the thermal budget and the complex photolithographic steps. The laser employed is a pulsed Nd-YAG lamp-pumped working at 1064 nm in nanosecond regime. The efficiency achieved was 18.0% (Jsc = 39.2 mA/cm2, Voc= 647mV, FF= 71.1%) on 280 micras thick 2.5 Ohmcm n-type FZ Si with a designated area of 9 cm2. The final efficciency achieved of the final "Cold" IBC cell was 20% (Jsc= 40.5 mA/cm2, Voc = 650 mV and FF = 76.4%)) using a pulsed Nd:YVO4 Laser operating at 355 nm (UV). The total fabrication process was carried out at low temperatures (below 400 ºC) avoiding the high-temperature difussion processes.El objetivo de este trabajo de tesis es el de la fabricación de células solares de alta eficiencia de tipo IBC (interdigitadas y contactadas en la parte posterior) a baja temperatura y bajo coste. En esta tesis se propone un nuevo concepto de fabricación simple y elegante que se ha llevado a cabo de manera exitosa resultado en la fabricación de dichas células como prueba de concepto.Para llevar a cabo este propósito, la investigación se ha focalizado en el estudio y aplicación de procesos a baja temperatura como la técnica de depósito de capas a nivel atómico (ALD) y el depósito químico en fase vapor con plasma (PECVD). También se ha desarrollado un proceso basado en el dopado láser utilizando capas dieléctricas para formar regiones dopadas p+ y n+ en el sustrato de silicio cristalino. Estas regiones altamente dopadas, están formadas siguiendo una estructura de puntos y utiliza Al2O3 y a-SiCx (n) como fuente de aluminio y fósforo respectivamente. Se ha realizado un estudio detallado con la finalidad de encontrar los parámetros del láser que proporcionen el mejor comportamiento eléctrico de las uniones p+/n y n+/p formadas. Para obtener las capas dieléctricas que mejor cumple con estas finalidades se ha realizado un estudio exhaustivo que optimiza el depósito de Al2O3 en términos de temperatura, tiempo y grosor de la capa.Con la finalidad de fabricar las células de tipo IBC "frías", primero se has desarrollado las primeras células solares de tipo IBC sobre c-Si (FZ) de tipo p realizando una difusión convencional de fósforo en horno a alta temperatura y se ha combinado con el dopado con láser . Se ha utilizado un "stack n" formado por a-SiCx(i)/a-Si(n)/a-SiCx para pasivar la superficie previamente difundida y como fuente de átomos de fósforo para formar regiones puntuales fuertemente dopadas n++ (emisores selectivos) después del procesado láser. Por otro lado un "stack p" formado por Al2O3/ a-SiCx provee de átomos de aluminio para crear las regiones puntuales p++ a la vez que pasiva la superficie del silicio. Como resultado se ha obtenido una eficiencia del 18.7% (Jsc= 39.1 mA/cm2, Voc= 638 mV, FF= 75.3%) .La primera célula IBC "fria" se ha obtenido después de eliminar la difusión convencional de fósforo y reestructurar los pasos de fabricación con la finalidad de eliminar procesos a alta temperatura y reducir pasos fotolitográficos que añaden complejidad al proceso. Para la realización de los contactos de emisor y base se ha utilizado un láser pulsado de 1064 nm (Nd-YAG en régimen de nanosegundos) . Se ha obtenido una eficiencia de 18% (Jsc = 39.2 mA/cm2, Voc= 647mV, FF= 71.1%) en c-Si tipo n (FZ) de 280µm, 2.5 Ocm y un área de 9 cm2. Finalmente, la realización de los contactos de la célula utilizando un láser de 355 nm (Nd:YVO4) ha permitido conseguir células solares IBC con eficiencias del 20% (Jsc= 40.5 mA/cm2, Voc = 650 mV and FF = 76.4%) . La técnica de dopado láser, junto con los depósitos de capas dieléctricas a baja temperatura a demostrado ser viable para la fabricación de células solares de tipo IBC de alta eficiencia a bajas temperaturas ( <400 C) y bajo coste.Postprint (published version

TCO-free low-temperature p+ emitters for back-junction c-Si solar cells

In this work, we report on the fabrication and characterization of n-type c-Si solar cells whose p+ emitters are based on laser processed aluminum oxide/silicon carbide (Al2O3/SiCx) films. The p+ emitter is defined at the rear side of the cell and it consists of point-like laser-diffused p+ regions with a surface charge induced emitter in between based on the high negative charge located at the Al2O3/c-Si interface. These emitters are fabricated at low temperature (1000 nm) that reach the rear surface of the cell resulting in an excellent back reflector. We fabricated solar cells with distance between p+ regions or pitch ranging from 200 to 350 µm with a front surface based on silicon heterojunction technology. Best efficiency (18.1%) is obtained for a pitch of 250 µm as a consequence of the trade-off between Voc and FF values.Peer ReviewedPostprint (published version

A CubeSAT payload for in-situ monitoring of pentacene degradation due to atomic oxygen etching in LEO

This paper reports and discusses the design and ground tests of a CubeSat payload which allows to measure, in-situ and in real time, the degradation of a polymer of electronic interest due to atomic oxygen etching in LEO. It provides real-time information on how the degradation occurs, eliminating the need to work with samples recovered once the mission has finished. The polymer, TIPS-Pentacene, is deposited on the surface of a microelectromechanical (MEMS) cantilever, which works as a resonator embedded in a Pulsed Digital Oscillator circuit. The mass losses in the polymer due to atomic oxygen corrosion produce variations in the resonant frequency of the MEMS, which is continuously sensed by the circuit and transmitted to the ground. This way, polymer mass losses around 10-12 kg can be detected during the mission. The payload is a part of the 3Cat-1 mission, a nano-satellite aimed at carrying out several scientific experiments.Peer ReviewedPostprint (author's final draft

Textured PDMS films applied to thin crystalline silicon solar cells

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Front surface texturization is a standard procedure used to improve optical properties of photovoltaic devices. In some particular cases, such as when dealing with ultrathin substrates, common texturization techniques can become unpractical or even unfeasible. Texturized polymer films applied on top of such devices may be used as an alternative. In this article, we report on the development of textured polydimethylsiloxane (PDMS) films to be placed on top of planar crystalline silicon solar cells based on thin substrates (=40 µ m). The PDMS polymer is deposited onto a rough surface (conventional random pyramid textured silicon), cured and detached from it. By scanning electron microscope images, we demonstrate that the dilution of PDMS into toluene helps in a better replica of the master surface. Next, we apply the optimized PDMS films on top of dummy samples based on 10, 20, and 40 µm thick crystalline silicon (c-Si) substrates whose reflectance is significantly reduced after placing the PDMS films. Accurate optical simulations indicate that the optical improvement comes from three mechanisms: higher light transmission into the device, lower reflectance at the c-Si surface, and better light trapping properties at the thin c-Si absorber. Experimental verification of the optical improvement with texturized PDMS films is reported based on 40 µ m thick solar cell, where a short-circuit current density gain of 1.7 mA/cm 2 is observed.This work was funded by MINECO from Spanish government under projects TEC2017-82305-R, ENE2016-78933-C4-1-R, ENE2017-87671-C3-2-R. The work was also supported in part by project REFER COMRDI15-1-0036 funded by ACCIÓ and the European Regional Development Fund (FEDER).Peer ReviewedPostprint (published version

Informe sobre la estabilidad del cimborrio de la iglesia de San Juan de los Reyes, Toledo

La iglesia de San Juan de los Reyes cuenta con uno de los primeros cimborrios del gótico tardío español. La iglesia fue proyectada por Juan Guas y Enrique Egas; sobre el proyecto del cimborrio, en el Museo del Prado se conserva un dibujo atribuido al primero. Juan Guas muere antes de acometer la obra del cimborrio y se produjo (por causas que los historiadores no han conseguido aclarar del todo) un cambio en el proyecto. El cimborrio finalmente construido parece deberse a Simón de Colonia. El cimborrio, en realidad un cuerpo de luces, presenta sus ventanales cegados; sólo en dos de ellos hay abiertas dos pequeñas ventanas. Por el interior los paños cegados se han pintado en trampantojo, simulando los maineles y decoración de un ventanal gótico. Se desconoce cuándo se cegaron los ventanales y la razón por la que se llevó a cabo esta operación. El arquitecto Javier Contreras, encargado del Proyecto de Restauración de las fachadas de la Iglesia de San Juan de los Reyes, ha considerado la posibilidad de volver a abrir los ventanales, devolviendo al cimborrio su función original de "linterna" del espacio interior. En la tradición de la construcción de fábrica, el cegar los huecos era una operación habitual de consolidación cuando había problemas de estabilidad. El objetivo principal de este informe es, pues, estudiar la posibilidad de abrir de nuevo los ventanales del cimborrio

Glucose-Insulin regulator for type 1 diabetes using high order neural networks

In this paper a Glucose-Insulin regulator for Type 1 Diabetes using artificial neural networks (ANN) is proposed. This is done using a discrete recurrent high order neural network in order to identify and control a nonlinear dynamical system which represents the pancreas? beta-cells behavior of a virtual patient. The ANN which reproduces and identifies the dynamical behavior system, is configured as series parallel and trained on line using the extended Kalman filter algorithm to achieve a quickly convergence identification in silico. The control objective is to regulate the glucose-insulin level under different glucose inputs and is based on a nonlinear neural block control law. A safety block is included between the control output signal and the virtual patient with type 1 diabetes mellitus. Simulations include a period of three days. Simulation results are compared during the overnight fasting period in Open-Loop (OL) versus Closed- Loop (CL). Tests in Semi-Closed-Loop (SCL) are made feedforward in order to give information to the control algorithm. We conclude the controller is able to drive the glucose to target in overnight periods and the feedforward is necessary to control the postprandial period

Diseño de un regulador no lineal por bloques para el sistema glucosa-insulina utilizando redes neuronales de alto orden

En este trabajo se propone un algoritmo de control en lazo cerrado para el control automático de la diabetes tipo 1 basado en la identificación de sistemas no lineales con redes neuronales artificiales y mediante la regulación basada en la forma controlable no lineal por bloques. Como paciente virtual se utiliza el modelo de Hovorka al que se conecta el algoritmo de control utilizando prealimentación procedente de la terapia prescrita con insulina y un módulo de seguridad para evitar las hipoglucemias. El identificador neuronal es entrenado en línea con un filtro de Kalman extendido con una función de activación definida por la tangente hiperbólica. El controlador no lineal por bloques se basa en la estructura de la red neuronal, cuya salida es la propuesta de dosificación de insulina antes de prealimentación y módulo de seguridad. El algoritmo presenta un peso que se interpreta como una ganancia de controlabilidad. La glucosa del paciente está condicionada al valor de la ganancia, se definen tres ensayos con diferentes valores: ensayo A (10?3); ensayo B (7 · 10?4) y ensayo C (9 · 10?3). El valor del peso de controlabilidad condiciona la cantidad de insulina propuesta por el controlador de forma directa en el paciente virtual medio del modelo de Hovorka

Quality of life and oral health in elderly

We want to assess quality of life in elderly patients in relation to the number of remaining teeth, the number of ingested drugs and xerostomía and to determine the correlation between an increased intake of drugs and a greater feeling of dry mouth and to know the most commonly used measures to control xerostomia. 30 subjects aged between 65 and 95 years (14 males, 16 females) completed the OHIP questionnaire to determine quality of life. For oral status, the number of remaining teeth according to WHO criteria and xerostomia using the xerostomia index (XI) were studied. In cases of dry mouth sensation, the measures to alleviate it were asked. The average quality of life according to the OHIP rate is 19.23 (Dt = 10.58), being 56 the worst quality of life. The Pearson correlation coefficient indicates that quality of life is not related to the number of remaining teeth (r = -0.046; p = 0.810) nor the number of ingested drugs (r = 0.226; p = 0.23) but a greater sensation of dry mouth is related to a poorer quality of life (r = 0.678; p = 0.230). There is no association between the number of ingested drugs and the xerostomia index (r = 0.144; p = 0.447). The most frequently measures used against dry mouth were drinking water (21 subjects) and sugarless candies (15 subjects). Quality of life is not related to the number of remaining teeth nor the number of ingested drugs. However, a higher level of xerostomia was significantly associated with a poorer quality of life. There is no association between the number of drugs ingested and xerostomia index. Sugarless candies and drinking water are the more frequently used measures to alleviate dry mouth

Oral microbiome and systemic antineoplastics in cancer treatment:a systematic review

Oral mucositis is one of the most common side effects in cancer patients receiving systemic antineoplastics. However, the underlying biological mechanisms leading to this condition are still unclear. For this reason, it has been hypothesised that systemic antineoplastics may cause an imbalance on the oral microbiota that subsequently triggers oral mucosa damage. A systematic review was performed following the PRISMA protocol and the PICO question established was: patients diagnosed with cancer, who are candidates for receiving systemic antineoplastics (P=Patients), that undergo oral microbiome determinations (I=Intervention), before and after systemic antineoplastics administration (C=Comparison), to analyse changes in the oral microbiome composition (O=Outcome). The bibliographic search was carried out in PubMed and other scientific repositories. Out of 166 obtained articles, only 5 met eligibility criteria. Acute myeloid leukaemia (AML) was the most frequent type of cancer (40 %) among the participants. Only one of the studies included a control group of healthy subjects. Heterogeneity in the protocols and approaches of the included studies hindered a detailed comparison of the outcomes. However, it was stated that a decrease in bacteria ? diversity is often associated with oral mucositis. On the other hand, fungal diversity was not associated with oral mucositis although ? diversity was lower at baseline on patients developing oral candidiasis. There is insufficient scientific evidence of oral microbiological changes in patients undergoing systemic antineoplastics. Further investigations ought to be carried out to identify microorganisms that might play a key role in the pathogenesis of oral mucosa damage in patients undergoing systemic antineoplastics

Acute and chronic effects of magnetic microparticles used in lake restoration on Daphnia magna and Chironomus sp.

Magnetic microparticles (MPs) have been recently proposed as a new and promising tool for restoring eutrophicated inland waters. In this study, we analyzed the acute and chronic effects of iron (Fe) MPs on Daphnia magna and on the benthic macroinvertebrate Chironomus sp. The endpoint in the acute toxicity tests was immobilization. In the chronic toxicity tests the offspring production (male and female) in D. magna and the mortality of larvae and pupae, and adult emergence in Chironomus sp. experiments were used as the endpoints. The concentration of MPs that caused 50% of immobilized individuals (EC50) in the acute toxicity test was much higher in D. magna (0.913 g Fe l-1) than in Chironomus sp. (0.445 g Fe l-1), which is likely to be the result of differences in the lifestyle of these organisms, planktonic and benthic respectively. Considering the regular dose of MPs that could be used in a restoration plan, slight effects on organism immobilization are expected. The results of chronic toxicity tests in D. magna showed that in presence of dissolved Fe (dFe), parthenogenetic reproduction was significantly affected, while no significant effect on mortality of larvae and pupae and on adult emergence was detected in Chironomus sp. test. Taking into account that long-term exposure is not likely to occur under the regular procedure of MPs, we conclude that MPs is a riskless (no toxic effect on planktonic and benthic organisms) and efficient (high P adsorption capacity) tool for lake restoration.This work was supported by Junta de Andalucía project P10-RNM-6630 (Proyectos de Excelencia, Spain), MINECO CTM 2013-46951-R projects (Spain) and by the European Founding for the Regional Development (Fondo Europeo de Desarrollo Regional, FEDER)