Debilidad institucional y experiencia anticrimen en México

This paper discusses the relation between the political situation in Mexico and the evolution of organized crime through an analysis of the case of the state of Michoacan. It proposes that the failure of the policies implemented to combat crime in the country can largely be explained by the adoption of a police-military strategy that does not address the structural causes of violence. In terms of methodology, research was conducted from an ethnographic perspective based on a detailed examination of the anti-crime policies of recent Mexican presidential administrations and their impact on Michoacán; an analysis framed in the perspective of historical institutionalism. The study concludes that by taking advantage of the weakness of the state and broad gaps in its authority, power groups such as organized crime have successfully embedded themselves in the wider society and the specific, concrete dynamics of the Mexican political system, especially at the level of local governments, making the problem of criminality a political matter, not one that concerns only the police or the military.El presente artículo analiza la relación entre corrupción política y narcotráfico en México, a partir del caso del estado de Michoacán. Se observa que, pese a la continuidad de la violencia, el Estado mexicano ha hecho poco por atender sistemáticamente sus causas estructurales. No se ha mejorado el estado de derecho, ni se han fortalecido las instituciones autónomas del Estado. Los poderes legislativos, en sus niveles locales y federales, continúan experimentando problemas de legitimidad y trasparencia en sus acciones. Asimismo, se han visto pocos avances democráticos en los gobiernos locales. Este artículo plantea la necesidad de mejorar la calidad democrática y la trasparencia de los gobiernos estatales de México y, especialmente, a escala municipal, como condiciones indispensables dentro de una estrategia estructural en contra del crimen organizado en el país

Challenges and opportunities for an efficiency boost of next generation Cu(In,Ga)Se2 solar cells: prospects for a paradigm shift

Cu(In,Ga)Se2 photovoltaic technology has notably progressed over the past years. Power conversion efficiencies above 23% were reached in spite of the polycrystalline nature of the absorber. Although efficiencies are still far from the practical limits, the material quality is approaching that of III?V compounds that yield the most efficient solar cells. The high carrier lifetime, low open circuit voltage deficit and external radiative efficiency in the single-digit percentage range suggest that the next efficiency boost may arise from the implementation of alternative device architectures. In this perspective paper, we describe the current challenges and pathways to enhance the power conversion efficiency of Cu(In,Ga)Se2 solar cells. Specifically, we suggest the use of non-graded absorbers, integration of charge selective contacts and maximization of photon recycling. We examine these concepts by a semi-empirical device modelling approach, and show that these strategies can lead to efficiencies of 29% under the AM1.5 global spectrum. An analysis of whether or not current state-of-the-art Cu(In,Ga)Se2 solar cells already benefit from photon recycling is also presented.This work received financial support partially from the Swiss State Secretary for Education, Research and Innovation (SERI) under contract number 17.00105 (EMPIR project HyMet) and from the Swiss Federal Office of Energy (SFOE) (SI/501614-01 “ImproCIS”). The EMPIR programme is co-financed by the Participating States and by the European Union's Horizon 2020 research and innovation programme

3-D modeling of perimeter recombination in GaAs diodes and its influence on concentrator solar cells

This paper describes a complete modelling of the perimeter recombination of GaAs diodes which solves most unknowns and suppresses the limitations of previous models. Because of the three dimensional nature of the implemented model, it is able to simulate real devices. GaAs diodes on two epiwafers with different base doping levels, sizes and geometries, namely square and circular are manufactured. The validation of the model is achieved by fitting the experimental measurements of the dark IV curve of the manufactured GaAs diodes. A comprehensive 3-D description of the occurring phenomena affecting the perimeter recombination is supplied with the help of the model. Finally, the model is applied to concentrator GaAs solar cells to assess the impact of their doping level, size and geometry on the perimeter recombination

Charge carrier lifetime fluctuations and performance evaluation of Cu(In,Ga)Se2 absorbers via time-resolved-photoluminescence microscopy

The open-circuit voltage (VOC) is the main limitation to higher efficiencies of Cu(In,Ga)Se2 solar cells. One of the most critical parameters directly affecting VOC is the charge carrier lifetime. Therefore, it is essential to evaluate the extent to which inhomogeneities in material properties limit the carrier lifetime and how postdeposition treatments (PDTs) and growth conditions affect material properties. Time-resolved photoluminescence (TRPL) microscopy is employed at conditions similar to one sun to study carrier lifetime fluctuations in Cu(In,Ga)Se2 with light (Na) and heavy (Rb) alkalis, different substrates, and grown at different temperatures. PDT lowers the amplitude of minority carrier lifetime fluctuations, especially for Rb-treated samples. Upon PDT, the grains’ carrier lifetime increases, and the analysis suggests a reduction in grain boundary recombination. Furthermore, lifetime fluctuations have a small impact on device performance, whereas VOC calculated from TRPL (and continuous-wave PL) agrees with device values within the limits of investigated PDT samples. Finally, up to about half a per cent external radiative efficiencies are experimentally determined from TRPL metrics, and internal radiative efficiencies are approximated. The findings demonstrate that the highest absorber material quality investigated is still limited by nonradiative recombination (grain or grain boundary) and is comparable to state-of-the-art absorbers.This work received financial support in part from the Swiss State Secretary for Education, Research and Innovation (SERI) under Contract No. 17.00105 (EMPIR project HyMet) and from the Swiss Federal Office of Energy (SFOE) (SI/501614-01 ‘‘ImproCIS''). The EMPIR programme was cofinanced by the Participating States and by the European Union's Horizon 2020 research and innovation programme

Lateral charge carrier transport in Cu(In,Ga)Se2 studied by time-resolved photoluminescence mapping

Electronic transport in a semiconductor is key for the development of more efficient devices. In particular, the electronic transport parameters carrier lifetime and mobility are of paramount importance for the modeling, characterization, and development of new designs for solar cells and optoelectronic devices. Herein, time-resolved photoluminescence mapping under low injection and wide-field illumination conditions is used to measure the carrier lifetime and analyze the lateral charge carrier transport in Cu(In,Ga)Se2 absorbers grown at different temperatures, on different substrates, and subject to different postdeposition treatments (PDT) with light or heavy alkalis. To estimate the carrier mobility, numerical simulations of carrier diffusion transport to areas of increased recombination (defects) are used, similarly as observed experimentally. Mobilities are found in the range of 10–50 cm2 V−1 s−1, and effective minority carrier lifetime between 100 and 800 ns resulting in carrier diffusion lengths of 2–9 μm depending on the sample. Finally, the factors limiting carrier mobility and the implications of carrier diffusion on the measured carrier lifetimes are discussed.This work received financial support partially from the Swiss State Secretary for Education, Research and Innovation (SERI) under contract number 17.00105 (EMPIR project HyMet) and from the Swiss Federal Office of Energy (SFOE) (SI/501614-01 ‘‘ImproCIS’’). The EMPIR program was cofinanced by the Participating States and by the European Union's Horizon 2020 research and innovation program

Influence of Ga back grading on voltage loss in low-temperature co-evaporated Cu(In,Ga)Se2 thin film solar cells

The performance of Cu(In,Ga)Se2 (CIGS) solar cells is limited by the presence of the highly recombinative CIGS/Mo interface. The recombination at the CIGS/Mo interface is influential for the open circuit voltage (VOC) in high quality CIGS absorbers with increased charge carriers diffusion length. A quantitative understanding of the role of the Ga back grading height (ΔGGI) in suppressing back interface recombination is needed. In this work, we take advantage of a low temperature process to modify the ΔGGI while keeping the composition in the notch and front regions almost unchanged. Improvement in both VOC deficit and time-resolved photoluminescence lifetime are observed with increasing ΔGGI. With a combination of back surface modification experiments and numerical simulations, we quantify a voltage loss in ungraded devices of approximately 100 mV solely from the back interface recombination. Nice agreement between simulation and experimental data is reached while constraining the values of possible diffusion lengths. Our results suggest that a ΔGGI of about 0.50 is required to effectively suppress the back interface recombination, highlighting the importance of grading control in high-performance CIGS solar cells and devices.Bundesamt für Energie, Grant/Award Number: SI/501614-01; Horizon 2020 Framework Programme, Grant/Award Number: EMPIR project HyMet; Swiss State Secretary for Education, Research and Innovation (SERI), Grant/Award Number: 17.00105 (EMPIR project HyMet

Impact of RbF and NaF postdeposition treatments on charge carrier transport and recombination in Ga-graded Cu(In,Ga)Se2 solar cells

Two key strategies for enhancing the efficiency of Cu(In,Ga)Se2 solar cells are the bandgap gradient across the absorber and the incorporation of alkali atoms. The combined incorporation of Na and Rb into the absorber has brought large efficiency gains compared to Na-containing or alkali-free layers. Here, transient absorption spectroscopy is employed to study the effect of NaF or combined NaF+RbF postdeposition treatments (PDT) on minority carrier dynamics in different excitation volumes of typical composition-graded Cu(In,Ga)Se2 solar cells. Electron lifetimes are found to be highly dependent on the film composition and morphology, varying from tens of nanoseconds in the energy notch to only ≈100 ps in the Ga-rich region near the Mo-back contact. NaF PDT improves recombination lifetimes by a factor of 2–2.5 in all regions of the absorber, whereas the effectiveness of the RbF PDT is found to decrease for higher Ga-concentrations. Electron mobility measured in the absorber region with large grains is promoted by both alkali PDTs. The data suggest that NaF PDT passivates shallow defect states (Urbach tail) throughout the Cu(In,Ga)Se2 film (including the interior of large grains), whereas the additional RbF PDT is effective at grain boundary surfaces (predominantly in regions with medium to low Ga-concentrations).Y.-H.C. thanks the Ministry of Education of Taiwan for her Ph.D. scholarship, Dr. Michael Sachs, and Dr. Carlota Bozal-Ginesta from Imperial College London for the fruitful discussions and aid on TA data. J.R.D. would like to thank the UKRI Global Challenge Research Fund project SUNRISE (EP/P032591/1). L.S. acknowledges funding from the European Research Council (H2020-MSCA-IF-2016, Grant No. 749231). This work also received financial support partially from the Swiss State Secretary for Education, Research and Innovation (SERI) under contract number 17.00105 (EMPIR project HyMet). The EMPIR programme is co-financed by the Participating States and by the European Union's Horizon 2020 research and innovation programme

Effect of Sb on the quantum efficiency of GaInP solar cells

The energy bandgap of GaInP solar cells can be tuned by modifying the degree of order of the alloy. In this study, we employed Sb to increase the energy bandgap of the GaInP and analyzed its impact on the performance of GaInP solar cells. An effective change in the cutoff wavelength of the external quantum efficiency of GaInP solar cells and an effective increase of 50 mV in the open-circuit voltage of GaInP/Ga(In)As/Ge triple junction solar cells were obtained with the use of Sb. Copyright © 2016 John Wiley & Sons, Ltd

Recent advances in biomedical photonic sensors: a focus on optical-fibre-based sensing

In this invited review, we provide an overview of the recent advances in biomedical pho tonic sensors within the last five years. This review is focused on works using optical-fibre technology, employing diverse optical fibres, sensing techniques, and configurations applied in several medical fields. We identified technical innovations and advancements with increased implementations of optical-fibre sensors, multiparameter sensors, and control systems in real applications. Examples of outstanding optical-fibre sensor performances for physical and biochemical parameters are covered, including diverse sensing strategies and fibre-optical probes for integration into medical instruments such as catheters, needles, or endoscopes.This work was supported by Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación (PID2019-107270RB-C21/AEI/10.13039/501100011033), and TeDFeS Project (RTC-2017- 6321-1) co-funded by European FEDER funds. M.O. and J.F.A. received funding from Ministerio de Ciencia, Innovación y Universidades of Spain under Juan de la Cierva-Formación and Juan de la Cierva-Incorporación grants, respectively. P.R-V. received funding from Ministerio de Educación, Cultura y Deporte of Spain under PhD grant FPU2018/02797

Light technology for efficient and effective photodynamic therapy: A critical review

Photodynamic therapy (PDT) is a cancer treatment with strong potential over well-established standard therapies in certain cases. Non-ionising radiation, localisation, possible repeated treatments, and stimulation of immunological response are some of the main beneficial features of PDT. Despite the great potential, its application remains challenging. Limited light penetration depth, non-ideal photosensitisers, complex dosimetry, and complicated implementations in the clinic are some limiting factors hindering the extended use of PDT. To surpass actual technological paradigms, radically new sources, light-based devices, advanced photosensitisers, measurement devices, and innovative application strategies are under extensive investigation. The main aim of this review is to highlight the advantages/pitfalls, technical challenges and opportunities of PDT, with a focus on technologies for light activation of photosensitisers, such as light sources, delivery devices, and systems. In this vein, a broad overview of the current status of superficial, interstitial, and deep PDT modalities - and a critical review of light sources and their effects on the PDT process - are presented. Insight into the technical advancements and remaining challenges of optical sources and light devices is provided from a physical and bioengineering perspective.This work was supported by Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación (PID2019-107270RB-C21/AIE/10.13039/501100011033