Review on Light Management by Nanostructures in Chalcopyrite Solar Cells

Light management has gained wide interest for various types of solar cells. This paper reviews the application of nanostructures for light management to chalcopyrite (CIGSe) type solar cells. Firstly, the relevance of light management for CIGSe solar cells will be introduced and applicable concepts of nanostructures for absorption enhancement discussed. The development of ultra- thin CIGSe solar cells and examples for nanoparticle fabrication techniques together with their chances and challenges for application to CIGSe will be presented. Particular attention will be paid to nanostructures that have been applied to CIGSe solar cells, revealing many theoretical and some experimental results. Metallic and dielectric nanostructures as well as intrinsic nanotextures will be covered. For the future, combined considerations of optical and electrical properties will gain in importance

Nano- and microlenses as concepts for enhanced performance of solar cells

Both metallic nanoparticles exhibiting plasmonic effects and dielectric nanoparticles coupling the light into resonant modes have shown successful applications to photovoltaics. On a larger scale, microconcentrator optics promise to enhance solar cell efficiency and to reduce material consumption. Here, we want to create a link between the concentrators on the nano- and on the microscale. From metallic nanospheres, we turn to dielectric ones and then look at increasing radii to approach the microscale. The lenses are investigated with respect to their interaction with light using three- dimensional simulations with the finite-element method. Resulting maps of local electric field distributions reveal the focusing behavior of the dielectric spheres. For larger lens sizes, ray tracing calculations, which give ray distributions in agreement with electric field intensities, can be applied. Calculations of back focal lengths in geometrical optics coincide with ray tracing results and allow insight into how the focal length can be tuned as a function of particle size, substrate refractive index, and the shape of the microlens. Despite the similarities we find for the nano- and the microlenses, integration into solar cells needs to be carefully adjusted, depending on the goals of material saving, concentration level, focal distance, and lens size

Gendered support to older parents: do welfare states matter?

The aim of this study is to examine the association of welfare state policies and the gendered organisation of intergenerational support (instrumental help and personal care) to older parents. The study distinguishes between support to older parents provided at least weekly, i.e. time-intensive and often burdening support, and supplemental sporadic support. Three policy instruments were expected to be associated with daughters' and sons' support or gender inequality in intergenerational support respectively: (1) professional social services, (2) cash-for-care payments and (3) legal obligations to provide or co-finance care for parents. The analyses based on the Survey of Health, Ageing and Retirement in Europe showed that daughters provided somewhat more sporadic and much more intensive support than sons throughout Europe. While about half of all children who sporadically supported a parent were men, this applied to only one out of four children who provided intensive support. Logistic multilevel models revealed that legal obligations were positively associated with daughters' likelihood of giving intensive support to parents but did not affect the likelihood of sons doing so. Legal obligations thus stimulate support in a gender-specific way. Both legal obligations and cash-for-care schemes were also accompanied by a more unequal distribution of involvement in intensive support at the expense of women. Social services, in contrast, were linked to a lower involvement of daughters in intensive support. In sum, the results suggest that welfare states can both preserve or reduce gender inequality in intergenerational support depending on specific arrangement

Influence of substrate and its temperature on the optical constants of CuIn1−xGaxSe2 thin films

We investigate the influence of substrate and its temperature on the optical constants of CuIn1−xGaxSe2 (CIGSe) thin films using the transfer-matrix method. The optical constants of a CIGSe layer on top of a transparent conducting oxide (TCO) layer were calculated considering the realistic optical constants of the TCO layer after CIGSe deposition. It was found that TCO substrates could influence the optical constants of CIGSe layers and that the ITO (Sn doped In2O3) substrate had a greater impact than IMO (Mo doped In2O3) for the CIGSe (x = 0.4) film when compared to a reference on bare glass substrate. Additionally, the varied substrate temperatures did not impact the optical constants of CGSe (x = 1). For CIGSe (x = 0.4), the refractive index n stayed relatively independent although at low temperature the grain size was reduced and the Ga/(Ga+In) profile was altered compared to that at high temperature (610 °C). In contrast, the extinction coefficient k at low temperature showed higher absorption at longer wavelengths because of a lower minimum bandgap (Eg,min) originating from reduced inter-diffusion of Ga–Se at a low substrate temperature

An Efficient Method for Calculating the Absorption Enhancement in Solar Cells with Integrated Plasmonic and Photonic Nanoparticles

We present a method for calculating the plasmonic and photonic enhancement of the absorption in solar cells. The method involves coupling between a transfer matrix method to describe light propagation in the layered stack and Mie theory for calculating the absorption and angular scattered field distribution from the nanoparticles. We also compare the method to rigorous simulations

Scanning near-field optical microscopy measurements and simulations of regularly arranged silver nanoparticles

Silver nanoparticles on a glass substrate are experimentally investigated by aperture scanning near-field optical microscopy (a-SNOM). To understand the experimental results, finite-element-method simulations are performed building a theoretical model of the a-SNOM geometry. We systematically vary parameters like aperture size, aluminum-coating thickness, tip cone angle, and tip-surface distance and discuss their influence on the near-field enhancement. All these investigations are performed comparatively for constant-height and constant-gap scanning modes. In the end, we establish a reliable and stable optical model for simulating a-SNOM measurements, which is capable of reproducing trends observed in experimental data

Bayesian mixed-effect models for the analysis of a series of FRAP images

The binding behavior of molecules in nuclei of living cells can be studied through the analysis of images from fluorescence recovery after photobleaching experiments. However, there is still a lack of methodology for the statistical evaluation of FRAP data, especially for the joint analysis of multiple dynamic images. We propose a hierarchical Bayesian nonlinear model with mixed-effect priors based on local compartment models in order to obtain joint parameter estimates for all nuclei as well as to account for the heterogeneity of the nuclei population. We apply our method to a series of FRAP experiments of DNA methyltransferase 1 tagged to green fluorescent protein expressed in a somatic mouse cell line and compare the results to the application of three different fixed-effects models to the same series of FRAP experiments. With the proposed model, we get estimates of the off-rates of the interactions of the molecules under study together with credible intervals, and additionally gain information about the variability between nuclei. The proposed model is superior to and more robust than the tested fixed-effects models. Therefore, it can be used for the joint analysis of data from FRAP experiments on various similar nuclei

Bayesian mixed-effect models for the analysis of a series of FRAP images

The binding behavior of molecules in nuclei of living cells can be studied through the analysis of images from fluorescence recovery after photobleaching experiments. However, there is still a lack of methodology for the statistical evaluation of FRAP data, especially for the joint analysis of multiple dynamic images. We propose a hierarchical Bayesian nonlinear model with mixed-effect priors based on local compartment models in order to obtain joint parameter estimates for all nuclei as well as to account for the heterogeneity of the nuclei population. We apply our method to a series of FRAP experiments of DNA methyltransferase 1 tagged to green fluorescent protein expressed in a somatic mouse cell line and compare the results to the application of three different fixed-effects models to the same series of FRAP experiments. With the proposed model, we get estimates of the off-rates of the interactions of the molecules under study together with credible intervals, and additionally gain information about the variability between nuclei. The proposed model is superior to and more robust than the tested fixed-effects models. Therefore, it can be used for the joint analysis of data from FRAP experiments on various similar nuclei

Expositions- und Gefährdungsabschätzung in der Bevölkerung von Bad Münder nach dem Eisenbahnunfall vom 09.09.2002

Am 09.09.2002 abends kollidierten im Bahnhof der Stadt Bad Münder zwei Güterzüge. Bei dem anschließenden sechsstündigen Brand geriet auch ein Kesselwagen mit Epichlorhydrin (ECH) in Brand. Potenziell waren etwa 19.000 Einwohner und ca. 700 Einsatzkräfte gegenüber ECH und weiteren Brandgasen exponiert. Ziel dieser Studie war es, die Verteilung der aufgetretenen ge-sundheitlichen Beschwerden und deren Einflussfaktoren zu untersuchen. Hierzu wurden eine randomisierte Bevölkerungsstichprobe, alle sich beim zuständigen Gesund-heitsamt Hameln-Pyrmont als betroffen gemeldete Personen (Selbstmelder) sowie Einsatzkräfte mittels Fragebogen angeschrieben. Aussagen für die Allgemeinbevölkerung sind nur aus dem An-gaben der Stichprobe möglich. Zielgrößen waren akute brandgasassoziierte Beschwerden (Nasen-, Augen-, Rachen-, Hautreizung) und unspezifische Unfallbegleiterscheinungen (Übelkeit, Kopf-schmerz, Nervosität, Schlafstörung) an den 3 Tagen nach dem Unfall (Expositionsphase). Diese Symptome wurden auch für eine Kontrollphase (3 Tage vor Ausfüllen des Fragebogens) erhoben, ferner die Aufenthaltsorte in den ersten 3 Tagen, soziodemographische Daten, die Lebensqualität und bestehende Erkrankungen. Zur Expositionsabschätzung diente der Hauptaufenthaltsort in den ersten 26 Stunden nach dem Unfall. Die Rücklaufquote in der Stichprobe betrug 63%, die Antworten von 445 Kindern und 1087 Er-wachsenen gingen in die Analyse ein. Bei Selbstmeldern (158 Kinder, 944 Erwachsene) und Einsatzkräften (342 Erwachsene) lagen die Rücklaufraten höher (bis zu 86%). Die Stichprobe ist als bedingt repräsentativ anzusehen, da signifikant weniger Probanden aus dem Norden von Bad Münder geantwortet hatten. Die Selbstmelder stellten ein hochselektioniertes und hochsymptoma-tisches Kollektiv dar. In allen Kollektiven waren Kopfschmerz und Rachenreizung die am häufigsten und Hautreizung und Übelkeit die am seltensten berichteten Symptome für die Expositionsphase. Stets lagen die Beschwerdehäufigkeiten und die Arztebesuche der Selbstmelder und der Einsatzkräfte signifikant und etwa um Faktor 2 höher als in der Stichprobe. Aus den Symptomangaben wurde die intraindi-viduelle Differenz zwischen Expositions- und Kontrollphase gebildet und diese Netto-Prävalenz in Abhängigkeit des Hauptaufenthaltsortes und weiterer Einflüsse analysiert. Eine rein deskriptiv / kartographische Auswertung ergab lediglich Hinweise für geringere Sym-ptomhäufigkeiten in den Ortschaften nördlich von Bad Münder (Luttringhausen / Nettelrede / Böbber, Nienstedt, Eimbeckhausen). In den multivariaten Regressionsanalysen zeigte sich für die Stichprobe (Erwachsene) eine räumliche Häufung von brandgasassoziierten Symptomen für Hauptaufenthaltsorte nahe der Unfallstelle (Klein Süntel, Flegessen, Hachmühlen, Hasperde, Bad Münder südost, - südzentral, - nordost, -nordwest). Keine räumliche Assoziation fand sich für Un-fallbegleiterscheinungen, ebenso wenig für die Unfallbeschwerden der Selbstmelder und der Kol-lektive der Kinder. Für die Einsatzkräfte stieg das Risiko brandgasassoziierter Beschwerden mit der Einsatzdauer am Unfallort an. Als weitere Prädiktoren für das Auftreten von Symptomen erga-ben sich das (weibliche) Geschlecht, bestehende allergisch / asthmatische Vorerkrankungen (v.a. für die Kinder) und eine erniedrigte Lebensqualität. Nach diesen Ergebnisen waren die nahe der Unfallstelle gelegenen Ortsteile pozentiell höher durch Brandgase belastet. Inwieweit diese Belastungen durch ECH, dessen Folgeprodukte oder Brandga-se verursacht wurden, kann nicht geklärt werden, ebenso wenig, ob die selbst berichteten Sym-ptome auf eine erhöhte Exposition oder eine erhöhte psychosoziale Wahrnehmung zurückzuführen sind. Weitere Aufschlüsse hierüber können möglicherweise die Ergebnisse des Humanbiomonito-rings liefern