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Research Interests: Materials Science, Nanoparticle, Transmission Electron Microscopy, Mathematical Sciences, Conducting Polymer, and 9 moreSolid State electronic devices, Physical sciences, Scanning Force Microscopy, X ray diffraction, Electrical Properties, Organic Solar Cell, Structural Properties, Atomic Force Microscope, and Active Layer
Zinc/air batteries are convenient energy storage devices for both small and massive applications. While future perspectives indicate the need for low‐cost components and sustainable fabrication processes, the battery performance is in... more
Zinc/air batteries are convenient energy storage devices for both small and massive applications. While future perspectives indicate the need for low‐cost components and sustainable fabrication processes, the battery performance is in part controlled by the kinetics of the oxygen reduction reaction (ORR), which typically involves transition metals as catalysts. In this context, we prepare a series of metal‐free water‐based carbon inks, which are tested for their catalytic performance, once being deposited on a gas‐diffusion substrate, in the air cathode of a simple battery prototype. The inks contain a variety of well‐defined carbon nanomaterials and additives, exhibiting different physicochemical properties that critically influence the interaction with the gas diffusion hydrophobic substrate. The intrinsic ORR catalytic activity of the ink material is also analysed on a glassy carbon electrode by the rotating ring‐disc electrode (RRDE) method and specific capacitance measurements. The discharge capacity on our zinc/air battery prototype well correlates with the intrinsic catalytic activity in the RRDE. However, only the activity in the RRDE does not actually assure the performance on the commercial cathode of the prototype, since other chemical compatibility issues play a role. Thus, we highlight the importance of catalyst testing, not only on the RRDE, but also under realistic device conditions.This article is protected by copyright. All rights reserved.
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ABSTRACT Stability of emerging organic and hybrid photovoltaic solar cells is still the main drawback for a market penetration of this technology. In this article, a study on the photodegradation of standard architecture P3HT:PCBM organic... more
ABSTRACT Stability of emerging organic and hybrid photovoltaic solar cells is still the main drawback for a market penetration of this technology. In this article, a study on the photodegradation of standard architecture P3HT:PCBM organic solar cells as a function of the incident radiation wavelength is presented. The organic solar cells were tested without encapsulation in order to accelerate the degradation process. By analyzing the evolution of power conversion efficiency and short circuit current as a function of the incident energy and number of photons, it was found that blue (400–510 nm) and ultraviolet (310– 410 nm) wavelengths are the most harmful, latter being the radiation that induces a faster degradation of the devices. However, the additional contribution of the blue wavelength to degradation represents a significant problem, since this radiation generates an important part of the photocurrent. While adequate filters could avoid the UV degradation without a significant decrease in the organic solar cell performance , the impact of blue radiation reduction poses a more difficult challenge.
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Research Interests: Engineering, Physics, Condensed Matter Physics, Art, Statistical Physics, and 14 moreMedicine, Critical phenomena, Mathematical Sciences, Power Law, Physical sciences, Quenched Disorder, Physical, Steady state, Fourier transform, Irreversible Thermodynamics, Autocorrelation Function, Exponential Function, Functional Dependency, and Relaxation Time
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In this work the electrostatic properties of poly(3-octylthiophene) thin films have been studied on a nanometer scale by means of electrostatic force microscopy and Kelvin probe microscopy (KPM). The KPM images reveal that different... more
In this work the electrostatic properties of poly(3-octylthiophene) thin films have been studied on a nanometer scale by means of electrostatic force microscopy and Kelvin probe microscopy (KPM). The KPM images reveal that different surface contact potential domains coexist on the polymer surface. This result, together with additional capacitance measurements, indicates that the potential domains are related to the existence of dipoles due to different molecular arrangements. Finally, capacitance measurements as a function of the tip-sample bias voltage show that in all regions large band bending effects take place.
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Charge separation is a critical process for achieving high efficiencies in organic photovoltaic cells. The initial tightly bound excitonic electron-hole pair has to dissociate fast enough in order to avoid photocurrent generation and thus... more
Charge separation is a critical process for achieving high efficiencies in organic photovoltaic cells. The initial tightly bound excitonic electron-hole pair has to dissociate fast enough in order to avoid photocurrent generation and thus power conversion efficiency loss via geminate recombination. Such process takes place assisted by transitional states that lie between the initial exciton and the free charge state. Due to spin conservation rules these intermediate charge transfer states typically have singlet character. Here we propose a donor-acceptor model for a generic organic photovoltaic cell in which the process of charge separation is modulated by a magnetic field which tunes the energy levels. The impact of a magnetic field is to intensify the generation of charge transfer states with triplet character via inter-system crossing. As the ground state of the system has singlet character, triplet states are recombination-protected, thus leading to a higher probability of succe...
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Organic solar cells (OSCs) have increased their power conversion efficiency above 18% thanks to the use of non-fullerene acceptors in binary or ternary blends or in tandem configurations. In this article, a study on the lifetime of... more
Organic solar cells (OSCs) have increased their power conversion efficiency above 18% thanks to the use of non-fullerene acceptors in binary or ternary blends or in tandem configurations. In this article, a study on the lifetime of P3HT:O-IDTBR bulk heterojunction OSCs on ITO-free flexible substrates is presented. A direct comparison of glass–glass and plastic–plastic encapsulation performance, with a special focus on its effect on the lifetime of the devices after degradation procedures, has been carried out complying with the ISOS protocols for organic photovoltaic devices. The manufactured OSCs with 1 cm2 active layer have power conversion efficiencies ranging from 1.9 to 3.4% depending on the encapsulant material, encapsulation process, and substrate. An exponential degradation rate has been found, with a similar functional behavior for glass and plastic differing in the degradation constants, which ranges from k = 0.01 to 0.002 h−1. Only in one case, the ISOS-T3 essay for plast...
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Perovskite solar cells have progressed very steadily, reaching power conversion efficiencies (PCE) beyond 20% while also improving their lifetimes up to 10,000 h. A large number of cell architecture and materials for active, transporting... more
Perovskite solar cells have progressed very steadily, reaching power conversion efficiencies (PCE) beyond 20% while also improving their lifetimes up to 10,000 h. A large number of cell architecture and materials for active, transporting and electrode layers have been used, either in blends or in nanostructured layers. In this article, a set of perovskite solar cells have been designed, fabricated and characterized with special focus on their lifetime extension. The inclusion of 5-amino-valeric acid iodide (5–AVAI) as interlayer in a methyl-amino lead-iodide (MAPI) perovskite solar cell has provided additional stability in cells with PCE > 10% and T80 = 550 h. Experiments for up to 1000 h with solar cells at maximum power point under continuous illumination with solar simulator have been carried out (1 kW/m2, AM1.5G, equivalent to more than six months of outdoor illumination in locations such as Southeast Spain, with an average irradiation of 1900 kWh/m2/year). The addition of mo...
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Research Interests: Engineering, Materials Science, Chemistry, Physical Chemistry, Technology, and 14 moreMaterials Chemistry, Materials, Morphology, Chemical Physics, Molecular Dynamics, Polymer, Physical sciences, CHEMICAL SCIENCES, Glass Transition, GROMACS, Science Technology, Scattering, Charge Transport, and Neutron Scattering
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Research Interests: Engineering, Environmental Science, Materials Science, Solar Cell, Dye Sensitized Solar Cells, and 15 moreLife Cycle Assessment, Sensitivity Analysis, Solar Cells, Manufacture, Environmental Technology, Physical sciences, Deposition, Environmental Assessment, Life Cycle, Ecotoxicity, Environmental Impact, CHEMICAL SCIENCES, Perovskite, Environmental Impact Analysis, and Photovoltaic Technology
ABSTRACT This article presents a model to calculate the impact on the grid of the injection of electricity generated from photovoltaic systems. The methodology combines the use of Geographical Information System tools to classify the... more
ABSTRACT This article presents a model to calculate the impact on the grid of the injection of electricity generated from photovoltaic systems. The methodology combines the use of Geographical Information System tools to classify the optimal locations for the installation of photovoltaic systems with the calculation of the impact into microgrids of the electricity generated in such locations. The case study is focused on Murcia region, in South-east Spain, and on medium size photovoltaic systems. The locations have been selected from a Geographical Information System database including several parameters, and evaluated and classified using a fuzzy version of the multicriteria decision method called Technique for Order Preference by Similarity to Ideal Solution. In order to obtain the weights for the criteria used in the evaluation, the Analytic Hierarchy Process has been used. Finally, using meteorological data from a small set of possible locations, the impact on the grid arising from the injection of power generated from photovoltaic systems that are connected to the grid via a module implementing different control electronic strategies has been calculated. Different electronic control strategies have been modeled to demonstrate that stabilization of the electrical parameters of a microgrid can be obtained within 500 ms in all cases, even when a relatively large power surge, or slower variations, are injected into the grid from the medium size photovoltaic systems.
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... Nieves Espinosa a , Corresponding Author Contact Information , E-mail The Corresponding Author , Rafael García-Valverde a , Antonio Urbina a , b , Frank Lenzmann c , Matthieu Manceau d , Dechan Angmo d , Frederik C. Krebs d. ...
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A study of the molecular structure of regio-regular bulk poly-3-octyl-thiophene (P3OT) and poly-3-hexyl-thiophene (P3HT) and the phase transitions during heating and cooling scans in a temperature range of–158–773° C has been performed by... more
A study of the molecular structure of regio-regular bulk poly-3-octyl-thiophene (P3OT) and poly-3-hexyl-thiophene (P3HT) and the phase transitions during heating and cooling scans in a temperature range of–158–773° C has been performed by means of calorimetry of ...
Research Interests: Engineering, Materials Science, Incidence Geometry, Synchrotron Radiation, Solar Energy Materials, and 13 moreThin Film, Physical sciences, Phase transition, Scanning Force Microscopy, CHEMICAL SCIENCES, Grazing, Glass Transition, Scattering, Organic Solar Cell, Low Temperature, Calorimetry, Information Presentation, and Molecular Structure
Research Interests: Engineering, Materials Science, Chemistry, Nanoelectronics, Glass, and 15 moreMorphology, Organic solar cells, Organic Electronics, Mesoscopic Physics, Casting, Nanostructure, Optical Properties, Morphological Variation, CHEMICAL SCIENCES, Ozone, Irradiation, Organic Solar Cell, Film Thickness, Contact Stress, and Optical Absorption
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Abstract The changes in morphology and electronic properties of Poly-3-octyl-thiophene (P3OT) thin films produced by UV/ozone exposure have been studied using Scanning Force Microscopy techniques. The layered structures associated to... more
Abstract The changes in morphology and electronic properties of Poly-3-octyl-thiophene (P3OT) thin films produced by UV/ozone exposure have been studied using Scanning Force Microscopy techniques. The layered structures associated to crystalline P3OT domains on the polymer film show a better resilience to the degradation than the amorphous polymer background. In addition, the effect of the UV irradiation and ozone exposure on the electronic properties (contact potential, capacitance and conductivity) of the thin films is studied, finding that the degradation process of the electronic properties of these crystalline structures is different to those of the amorphous polymer background.
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The morphology and mechanical properties of poly-(3-octylthiophene) P3OT films thin has been studied by scanning force microscopy techniques. On these films we find self-assembled layered structures that appear regardless of the... more
The morphology and mechanical properties of poly-(3-octylthiophene) P3OT films thin has been studied by scanning force microscopy techniques. On these films we find self-assembled layered structures that appear regardless of the preparation conditions, that is, spin-coating or drop-casting, of the solvent concentration or of the type of substrate. Using the drop-casting method for sample preparation these layered structures are hardly
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Abstract Mixtures of poly (3-octylthiophene)(P3OT) with graphite nanoparticles have been investigated by scanning force microscopy (SFM) techniques. The morphology as well as the mechanical and electrical properties of the blends has been... more
Abstract Mixtures of poly (3-octylthiophene)(P3OT) with graphite nanoparticles have been investigated by scanning force microscopy (SFM) techniques. The morphology as well as the mechanical and electrical properties of the blends has been characterized at the ...
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Variable transmission applications for light control or energy saving based on electrochromic materials have been successfully applied in the past in the building, sports, or automotive fields, although lower costs and ease of... more
Variable transmission applications for light control or energy saving based on electrochromic materials have been successfully applied in the past in the building, sports, or automotive fields, although lower costs and ease of fabrication, installation, and maintenance are still needed for deeper market integration. In this study, all-printed large area (900 cm2 active area) flexible electrochromic devices were fabricated, and an autoregulating self-power supply was implemented through the use of organic solar cells. A new perspective was applied for automotive light transmission function, where portability and mechanical flexibility added new features for successful market implementation. Special emphasis was placed in applying solution-based scalable deposition techniques and commercially available materials (PEDOT-PSS as an electrochromic material; vanadium oxide, V2O5, as a transparent ion-storage counter electrode; and organic solar modules as the power supply). A straightforwa...
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The integration of photovoltaic technologies into greenhouse envelopes appears to be an innovative and environmentally-friendly way to supply their various energy demands. However, the effect on the inner growing conditions, especially on... more
The integration of photovoltaic technologies into greenhouse envelopes appears to be an innovative and environmentally-friendly way to supply their various energy demands. However, the effect on the inner growing conditions, especially on the temperature, must be assessed in order to effectively implement this solution. In this study, experimental temperature data were obtained over two years for four structures built with different photovoltaic technologies (mono-crystalline silicon, amorphous silicon, cadmium telluride, and an organic polymeric technology) and fitted to a thermal model in order to provide a comprehensive analysis of their potential utilization as a cover material in greenhouses. Additionally, the thermal effect of color in structures composed of several common construction materials (brick, wood, plasterboard and glass) was quantified and modelled, supplementing the thermal analysis of passive solutions for this application. In all cases, inner and ambient tempera...
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A new rechargeable Zn/PVA-KOH/Bi2O3 with coulombic efficiencies of 100% and energy efficiencies above 80% for a high number of cycles.
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Incident solar radiation modelling has become of vital importance not only in architectural design considerations, but also in the estimation of the energy production of photovoltaic systems. This is particularly true in the case of... more
Incident solar radiation modelling has become of vital importance not only in architectural design considerations, but also in the estimation of the energy production of photovoltaic systems. This is particularly true in the case of buildings with integrated photovoltaics (PV) systems having a wide range of orientations and inclinations defined by the skin of the building. Since solar radiation data at the plane of interest is hardly ever available, this study presents the analysis of two of the most representative transposition models used to obtain the in-plane irradiance using as input data the global and diffuse irradiation on the horizontal plane, which can be obtained by satellite-based models or ground measurements. Both transposition models are validated with experimental measurements taken in Murcia (southeast of Spain) and datasets provided by the photovoltaic geographical information system (PVGIS) and the National Renewable Energy Laboratory (NREL) for vertical surfaces ...
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Photovoltaic technology is progressing very fast, both in a new installed capacity, now reaching a total of more than 400 GW worldwide, and in a big research effort to develop more efficient and sustainable technologies. Organic and... more
Photovoltaic technology is progressing very fast, both in a new installed capacity, now reaching a total of more than 400 GW worldwide, and in a big research effort to develop more efficient and sustainable technologies. Organic and hybrid solar cells have been pointed out as a technological breakthrough due to their potential for low economical cost and low environmental impact; but despite impressive laboratory progress, the market is still beyond reach for these technologies, especially for perovskite-based technology. In this review, the historical evolution and relationship of efficiency and stability is addressed, including Life Cycle Assessment studies which provide a quantitative evaluation of environmental impacts in several categories, such as human health or freshwater ecotoxicity, with special focus on lead toxicity. The main conclusion is that there is no unsurmountable barrier for the massive deployment of photovoltaic systems with perovskite solar modules, if the stab...
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Photovoltaic electricity generation is growing at an almost exponential rate worldwide, reaching 400 GWp of installed capacity in 2018. Different types of installations, ranging from small building integrated systems to large plants,... more
Photovoltaic electricity generation is growing at an almost exponential rate worldwide, reaching 400 GWp of installed capacity in 2018. Different types of installations, ranging from small building integrated systems to large plants, require different maintenance strategies, including strategies for monitorization and data processing. In this article, we present three case studies at different scales (from hundreds of Wp to a 2.1 MWp plant), where automated parameter monitorization and data analysis has been carried out, aiming to detect failures and provide recommendations for optimum maintenance procedures. For larger systems, the data collected by the inverters provides the best source of information, and the cross-correlated analysis which uses these data is the best strategy to detect failures in module strings and failures in the inverters themselves (an average of 32.2% of inverters with failures was found after ten years of operation). In regards to determining which module ...
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The diverse socio-economic and environmental impacts that the set-up of a new photovoltaic installation has must be weighed carefully in order to reach the best possible solution. Among the different photovoltaic systems there are several... more
The diverse socio-economic and environmental impacts that the set-up of a new photovoltaic installation has must be weighed carefully in order to reach the best possible solution. Among the different photovoltaic systems there are several classification criteria, depending on the technology, application and the size of the modules that define them. The size (installed nominal capacity) stands out as an impartial and critical measure in the decision making process. In this article we use a multi-criteria decision making method to analyse the responses of five experts to a detailed questionnaire in which several different criteria are correlated with various photovoltaic installation sizes. The limitation associated to the low number of experts is addressed with a robustness and sensitivity analysis. With this study we seek first, to apply and demonstrate the feasibility of a methodology which combines technical information with multi-criteria decision making methods, and second, to o...
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Research Interests: Engineering, Technology, Renewable Energy, Consumption, Life Cycle Assessment, and 15 moreBatteries, Livelihood, Experience, Multicriteria Decision Analysis, Physical sciences, Greenhouse Gas, Cells, Science Technology, Energy and Fuels, Photovoltaic systems, ENERGIES, Solar Home Systems, Efficiencies, Life Cycle Analysis (LCA), and PV modules
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Organic photovoltaics are analysed for use within a photovoltaic greenhouse for combined crop growth and electricity production.
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Data mining techniques have been used on data collected from a photovoltaic system to predict its generation and performance. Nevertheless, up to date, this computing approach has needed the simultaneous measurement of environmental... more
Data mining techniques have been used on data collected from a photovoltaic system to predict its generation and performance. Nevertheless, up to date, this computing approach has needed the simultaneous measurement of environmental parameters that are collected by an array of sensors. This chapter presents the application of several computing learning techniques to electrical data in order to detect and classify the occurrence of failures (i.e. shadows, bad weather conditions, etc.) without using environmental data. The results of a 222kWp (CdTe) case study show how the application of computing learning algorithms can be used to improve the management and performance of photovoltaic generators without relying on environmental parameters.
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Carbon nanotubes have proved their enormous potential as a new advanced material. Their mechanical and electronic properties can be used to improve the properties of structural polymers and molecular electronic devices. It is necessary to... more
Carbon nanotubes have proved their enormous potential as a new advanced material. Their mechanical and electronic properties can be used to improve the properties of structural polymers and molecular electronic devices. It is necessary to improve the growth techniques towards a controlled, self-organized fabrication procedure in order to obtain useful applications. PECVD growth of aligned carbon nanotubes on different substrates is a promising technique which could lead to the first commercial applications.