Photovoltaic/thermal systems based on concentrating and non-concentrating technologies: Working fluids at low, medium and high temperatures

The present article provides an overview about photovoltaic/thermal systems categorised by the temperature of the working fluid: Low-temperature (lower than 60º C), medium-temperature (between 60 and 90º C) and hightemperature (higher than 90º C). Concerning photovoltaic/thermal-air systems for low-temperature use, the majority of studies involve building-integrated non-concentrating systems with phase change materials and working-fluid temperatures at around 30-55º C. Concerning low-temperature photovoltaic/thermal-water systems, a large number of studies are about non-concentrating configurations appropriate for building-integrated and, in general, domestic applications with working fluids at approximately 50–60º C. Regarding nonconcentrating photovoltaic/thermal systems for medium-temperature use, a large number of references are appropriate for industrial and domestic applications (working fluids: air; water) with around 60-70º C workingfluid temperatures. The literature review about medium-temperature concentrating photovoltaic/thermal systems shows that the majority of investigations concern photovoltaic/thermal-water systems with concentration ratios up to 190X and working fluids at approximately 62-90º C, appropriate for domestic and waterdesalination applications. As for high-temperature concentrating photovoltaic/thermal systems, most of them have concentration ratios up to 1000X, involve parabolic concentrators and use water (as the working fluid) at around 100-250º C. Moreover, in the field of high-temperature photovoltaic/thermal systems, most of the configurations are appropriate for building and industrial applications, and consist of triple-junction or siliconbased photovoltaic/thermal cells. In light of the issues mentioned above, a critical discussion and key challenges (in terms of materials, efficiencies, technologies, etc.) are presented.The authors would like to thank ’’Ministerio de Economía y Competitividad’’ and “Ministerio de Ciencia e Innovación” of Spain for the funding (grant references ENE2016-81040-R and PID2019-111536RBI00). D. Chemisana thanks ’’Institució Catalana de Recerca i Estudis Avançats (ICREA)’’ for the ICREA Acadèmia award. Chr. Lamnatou is Lecturer of the Serra Húnter programme. Figures 1–6: reproduced with permission

Injection-dependent Minority Carrier Lifetime in Epitaxial Silicon Layers by Time-resolved Photoluminescence

AbstractTime-resolved photoluminescence (TRPL) is used to evaluate the injection-dependent effective minority carrier lifetime of high resistivity epitaxial silicon layers grown on highly doped CZ-Si substrates. Effective lifetimes ranging from 10μs to 200μs are estimated for excess carrier densities between 1x1017 cm-3 and 2x1016 cm-3. Standard models are used to separate the contribution from the different recombination mechanisms. The influence of the epitaxial layer and substrate parameters on the minority carrier effective lifetime measurement is discussed

International Expert Opinions and Recommendations on the Use of Melatonin in the Treatment of Insomnia and Circadian Sleep Disturbances in Adult Neuropsychiatric Disorders

Introduction: Insomnia and circadian rhythm disorders, such as the delayed sleep phase syndrome, are frequent in psychiatric disorders and their evaluation and management in early stages should be a priority. The aim of this paper was to express recommendations on the use of exogenous melatonin, which exhibits both chronobiotic and sleep-promoting actions, for the treatment of these sleep disturbances in psychiatric disorders.Methods: To this aim, we conducted a systematic review according to PRISMA on the use of melatonin for the treatment of insomnia and circadian sleep disorders in neuropsychiatry. We expressed recommendations for the use of melatonin in psychiatric clinical practice for each disorder using the RAND/UCLA appropriateness method.Results: We selected 41 studies, which included mood disorders, schizophrenia, substance use disorders, attention deficit hyperactivity disorders, autism spectrum disorders, neurocognitive disorders, and delirium; no studies were found for both anxiety and eating disorders.Conclusion: The administration of prolonged release melatonin at 2–10 mg, 1–2 h before bedtime, might be used in the treatment of insomnia symptoms or comorbid insomnia in mood disorders, schizophrenia, in adults with autism spectrum disorders, neurocognitive disorders and during sedative-hypnotics discontinuation. Immediate release melatonin at <1 mg might be useful in the treatment of circadian sleep disturbances of neuropsychiatric disorders

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Synthesis and characterizations of Ge nanocrystals based materials for optoelectronical application

Les nanomatériaux, grâce à leurs propriétés optiques et électroniques, peuvent être une opportunité pour le développement d'une nouvelle génération de cellules photovoltaïques à hauts rendements et bas coût. Les boîtes quantiques sous la forme de nanocristaux semi-conducteurs permettent de réaliser des matériaux à énergie de gap variable, propriété très recherchée pour un absorbeur solaire. Ce travail est consacré à l'élaboration et à la caractérisation de matériaux à base de nanocristaux de Ge dans différentes matrices. Une source à agrégats, procédé original de pulvérisation sous vide, a été étudiée pour synthétiser des nanoparticules de Ge. Cette technique de dépôt permet la formation de nanoparticules de Ge bien cristallisées (pour un substrat maintenu à température ambiante) et d'avoir un très bon contrôle de la taille de ces nanocristaux. Des caractérisations optiques de nanocristaux de Ge enfouis dans des matrices isolantes et semi-conductrices ont permis de démontrer la présence d’effet de confinement quantique dans ces cristaux et la possibilité de moduler leur énergie de gap sur une large gamme d'énergie entre 0,85 et 1,55 eV. Afin d’extraire et de collecter des charges photogénérées dans les nanocristaux, nous nous sommes intéressés au couple nanocristaux de Ge / matrice de ZnO:Al qui permet de séparer spatialement les photoporteurs (alignement en type II). La structure composée de nanocristaux de Ge recouverts d'une matrice de ZnO:Al sur un substrat de Si (p+), a permis de mettre en évidence un effet photovoltaïque pour lequel la génération de porteurs s'effectue uniquement dans les nanocristaux de Ge.The particular properties of nanomaterials can be an opportunity for developing a new low cost and a high efficient generation of solar cells. Semiconducting nanocrystals can be used as quantum dots to realize band gap engineering by varying the nanocrystals size. The subject of research is to synthesize a composite material based on Ge nanocrystals embedded in various matrices and perform characterizations. A nanocluster source, under vacuum sputtering setup, was used to synthesize Ge nanoparticles. The vapor phase condensation leads to the formation of well crystallized nanoparticles, for a deposition performed at room temperature. This synthesis method allows a good control of the nanocrystals size and the nanocrystals quantity inserted in the material. Optical properties of Ge nanocrystals embedded in insulating and semiconducting matrices were studied. We have demonstrated the quantum dot behavior of Ge nanocrystals. We have also shown the ability to modulate the nanocrystals band gap from 0.85 to 1.55 eV by varying the nanocrystals size and the potential barriers. Optoelectronical characterizations were performed to estimate the ability to extract and collect the carriers photogenerated in the Ge nanocrystals by light absorption. Ge nanocrystals in ZnO:Al matrix forms type-II quantum dots. This heterostructure is very interesting because it allows the spatial separation of the carriers while keeping the quantum confinement properties. We have brought out a photovoltaic effect with the structure p+-Si wafer / Ge nanocrystals / ZnO:Al matrix. We have also demonstrated that the carrier generation only occurs in the Ge nanocrystals

Synthesis and characterizations of Ge nanocrystals based materials for optoelectronical application

Les nanomatériaux, grâce à leurs propriétés optiques et électroniques, peuvent être une opportunité pour le développement d'une nouvelle génération de cellules photovoltaïques à hauts rendements et bas coût. Les boîtes quantiques sous la forme de nanocristaux semi-conducteurs permettent de réaliser des matériaux à énergie de gap variable, propriété très recherchée pour un absorbeur solaire. Ce travail est consacré à l'élaboration et à la caractérisation de matériaux à base de nanocristaux de Ge dans différentes matrices. Une source à agrégats, procédé original de pulvérisation sous vide, a été étudiée pour synthétiser des nanoparticules de Ge. Cette technique de dépôt permet la formation de nanoparticules de Ge bien cristallisées (pour un substrat maintenu à température ambiante) et d'avoir un très bon contrôle de la taille de ces nanocristaux. Des caractérisations optiques de nanocristaux de Ge enfouis dans des matrices isolantes et semi-conductrices ont permis de démontrer la présence d’effet de confinement quantique dans ces cristaux et la possibilité de moduler leur énergie de gap sur une large gamme d'énergie entre 0,85 et 1,55 eV. Afin d’extraire et de collecter des charges photogénérées dans les nanocristaux, nous nous sommes intéressés au couple nanocristaux de Ge / matrice de ZnO:Al qui permet de séparer spatialement les photoporteurs (alignement en type II). La structure composée de nanocristaux de Ge recouverts d'une matrice de ZnO:Al sur un substrat de Si (p+), a permis de mettre en évidence un effet photovoltaïque pour lequel la génération de porteurs s'effectue uniquement dans les nanocristaux de Ge.The particular properties of nanomaterials can be an opportunity for developing a new low cost and a high efficient generation of solar cells. Semiconducting nanocrystals can be used as quantum dots to realize band gap engineering by varying the nanocrystals size. The subject of research is to synthesize a composite material based on Ge nanocrystals embedded in various matrices and perform characterizations. A nanocluster source, under vacuum sputtering setup, was used to synthesize Ge nanoparticles. The vapor phase condensation leads to the formation of well crystallized nanoparticles, for a deposition performed at room temperature. This synthesis method allows a good control of the nanocrystals size and the nanocrystals quantity inserted in the material. Optical properties of Ge nanocrystals embedded in insulating and semiconducting matrices were studied. We have demonstrated the quantum dot behavior of Ge nanocrystals. We have also shown the ability to modulate the nanocrystals band gap from 0.85 to 1.55 eV by varying the nanocrystals size and the potential barriers. Optoelectronical characterizations were performed to estimate the ability to extract and collect the carriers photogenerated in the Ge nanocrystals by light absorption. Ge nanocrystals in ZnO:Al matrix forms type-II quantum dots. This heterostructure is very interesting because it allows the spatial separation of the carriers while keeping the quantum confinement properties. We have brought out a photovoltaic effect with the structure p+-Si wafer / Ge nanocrystals / ZnO:Al matrix. We have also demonstrated that the carrier generation only occurs in the Ge nanocrystals

Synthèse et caractérisations de matériaux composites à base de nanocristaux de Ge pour des applications optroniques

The particular properties of nanomaterials can be an opportunity for developing a new low cost and a high efficient generation of solar cells. Semiconducting nanocrystals can be used as quantum dots to realize band gap engineering by varying the nanocrystals size. The subject of research is to synthesize a composite material based on Ge nanocrystals embedded in various matrices and perform characterizations. A nanocluster source, under vacuum sputtering setup, was used to synthesize Ge nanoparticles. The vapor phase condensation leads to the formation of well crystallized nanoparticles, for a deposition performed at room temperature. This synthesis method allows a good control of the nanocrystals size and the nanocrystals quantity inserted in the material. Optical properties of Ge nanocrystals embedded in insulating and semiconducting matrices were studied. We have demonstrated the quantum dot behavior of Ge nanocrystals. We have also shown the ability to modulate the nanocrystals band gap from 0.85 to 1.55 eV by varying the nanocrystals size and the potential barriers. Optoelectronical characterizations were performed to estimate the ability to extract and collect the carriers photogenerated in the Ge nanocrystals by light absorption. Ge nanocrystals in ZnO:Al matrix forms type-II quantum dots. This heterostructure is very interesting because it allows the spatial separation of the carriers while keeping the quantum confinement properties. We have brought out a photovoltaic effect with the structure p+-Si wafer / Ge nanocrystals / ZnO:Al matrix. We have also demonstrated that the carrier generation only occurs in the Ge nanocrystals.Les nanomatériaux, grâce à leurs propriétés optiques et électroniques, peuvent être une opportunité pour le développement d'une nouvelle génération de cellules photovoltaïques à hauts rendements et bas coût. Les boîtes quantiques sous la forme de nanocristaux semi-conducteurs permettent de réaliser des matériaux à énergie de gap variable, propriété très recherchée pour un absorbeur solaire. Ce travail est consacré à l'élaboration et à la caractérisation de matériaux à base de nanocristaux de Ge dans différentes matrices. Une source à agrégats, procédé original de pulvérisation sous vide, a été étudiée pour synthétiser des nanoparticules de Ge. Cette technique de dépôt permet la formation de nanoparticules de Ge bien cristallisées (pour un substrat maintenu à température ambiante) et d'avoir un très bon contrôle de la taille de ces nanocristaux. Des caractérisations optiques de nanocristaux de Ge enfouis dans des matrices isolantes et semi-conductrices ont permis de démontrer la présence d’effet de confinement quantique dans ces cristaux et la possibilité de moduler leur énergie de gap sur une large gamme d'énergie entre 0,85 et 1,55 eV. Afin d’extraire et de collecter des charges photogénérées dans les nanocristaux, nous nous sommes intéressés au couple nanocristaux de Ge / matrice de ZnO:Al qui permet de séparer spatialement les photoporteurs (alignement en type II). La structure composée de nanocristaux de Ge recouverts d'une matrice de ZnO:Al sur un substrat de Si (p+), a permis de mettre en évidence un effet photovoltaïque pour lequel la génération de porteurs s'effectue uniquement dans les nanocristaux de Ge