Tin and Mixed Lead–Tin Halide Perovskite Solar Cells: Progress and their Application in Tandem Solar Cells

Metal halide perovskites have recently attracted enormous attention for photovoltaic applications due to their superior optical and electrical properties. Lead (Pb) halide perovskites stand out among this material series, with a power conversion efficiency (PCE) over 25%. According to the Shockley–Queisser (SQ) limit, lead halide perovskites typically exhibit bandgaps that are not within the optimal range for single-junction solar cells. Partial or complete replacement of lead with tin (Sn) is gaining increasing research interest, due to the promise of further narrowing the bandgaps. This enables ideal solar utilization for single-junction solar cells as well as the construction of all-perovskite tandem solar cells. In addition, the usage of Sn provides a path to the fabrication of lead-free or Pb-reduced perovskite solar cells (PSCs). Recent progress in addressing the challenges of fabricating efficient Sn halide and mixed lead–tin (Pb–Sn) halide PSCs is summarized herein. Mixed Pb–Sn halide perovskites hold promise not only for higher efficiency and more stable single-junction solar cells but also for efficient all-perovskite monolithic tandem solar cells.     

Incubation of PbSe Thin Films in a Tin(Ⅱ) Salt Aqueous Solution:Modification and Ion-Exchange Reactions

Topochemical ion-exchange reactions between solid micro-and nanostructured metal chalcogenides and aqueous salt solutions are generally used for formation of composite structures based on initial metal chalcogenides and products of their ion-exchange transformation.However,ion exchange has promises as a route to obtaining both composites and solid solutions based on the initial and the end chalcogenide phases.With the help of the ion-exchange technique,single-phase films of Pb_(1-x)Sn_xSe substitutional solid solutions with a tin content up to~2 at.%,which are promising for mid-and long-wavelength infrared radiation(IR)optoelectronics,have been obtained at the interface between PbSe polycrystalline thin films and SnCl_2 aqueous solutions containing sodium citrate.It has been shown that the pH value and temperature of the reaction system play an important role in the ion-exchange process.Incubation of lead selenide(PbSe)films in a tin(Ⅱ)salt aqueous solution also leads to their modification with oxygen-containing tin compounds to a depth of~3 nm.Differences in the film structure,such as changes in the coherent scattering region sizes and orientation of crystallites along the[220]direction,which arise during the contact with citrate-containing SnCl_2 solutions,have also been revealed.For the first time,an idea of the existence of a relatively wide reaction zone of an intragranular topochemical ion-exchange reaction in an aqueous solution,within which substitutional solid solutions can form in micro-and nanostructured systems,has been set forth.     

Solid-State Field-Assisted Ion Exchange (Ag → Na) in Soda–Lime Float Glass: Tin Versus Air Side

The application of a DC current allows fast (few minutes) Ag⁺ → Na⁺ ion exchange in soda–lime–silicate (SLS) glass. The effect of processing parameters, electric current, and treating time is studied on both air and tin sides of SLS float glass, and non-Fickian diffusion is revealed. It is shown that ion exchange kinetics are similar on both sides and the tempering process results in similar mechanical properties (crack formation probability after Vickers indentation, hardness, and Young's modulus). However, the structure/microstructure of the tin and air sides is hugely different. In particular, clear silver nanoclustering takes place on the tin side, resulting in ≈8 nm metallic particles in the vicinity of the surface. The formation of nanoparticles is also coupled with a deep structural reorganization of the amorphous network and the Q ⁿ units. The nanoparticles’ size decreases moving from the surface to the interior of the glass. Silver nanoparticles are also detected on the air side, although their density and size are largely reduced. Whereas the mechanical properties measured on the air and tin side are similar, significative differences are observed in terms of optical properties.     

Ageing drivers: storm in a teacup?

The purpose of this paper is to address two important issues regarding ageing drivers. First, there is a presumption in the road safety arena that the expected increase in the number of ageing drivers on the roads will lead to an increase in crashes. Second, despite extensive research on ageing drivers, especially on their increased vulnerability and reduced driving abilities, the most widely recommended road safety strategy relates to the control of their driving licenses. This presumption and the associated policy recommendation are based mainly on the higher relative crash risks associated with ageing drivers compared to their younger counterparts. This study, however, argues that the average crash risks obtained in previous studies provide only indirect information concerning these issues and any decision based on these results may produce unexpected outcomes. An analytical framework to examine the marginal effect of changing the driver mix on the roads is proposed and a simple empirical model is estimated as an illustration. In contrast to previous studies, we found that increasing the number of licenses issued to ageing drivers had only an insignificant impact on the number of fatal crashes on the roads, suggesting that the concern over ageing drivers may be a storm in a teacup.     

Caffeine in your drink: natural or synthetic?

Owing to possible adulteration and health concerns, it is important to discriminate between natural and synthetic food ingredients. A new method for compound-specific isotope analysis (CSIA) by coupling high-temperature reversed-phase liquid chromatography to isotope ratio mass spectrometry (HT-RPLC/IRMS) was developed for discrimination of natural and synthetic caffeine contained in all types of drinks. The analytical parameters such as stationary phase, column inner diameter, and column temperature were optimized for the separation of caffeine directly from drinks (without extraction). On the basis of the carbon isotope analysis of 42 natural caffeine samples including coffee beans, tea leaves, guaraná powder, and maté leaves, and 20 synthetic caffeine samples from different sources by high-temperature reversed-phase liquid chromatography coupled to isotope ratio mass spectrometry, it is concluded that there are two distinguishable groups of caffeine δ(13)C-values: one between -25 and -32‰ for natural caffeine, and the other between -33 and -38‰ for synthetic caffeine. Isotope analysis by HT-RPLC/IRMS has been applied to identify the caffeine source in 38 drinks. Four mislabeled products were detected due to added but nonlabeled synthetic caffeine with δ(13)C-values lower than -33‰. This work is the first application of HT-RPLC/IRMS to real-world food samples, which showed several advantages: simple sample preparation (only dilution), high throughput, long-term column stability, and high precision of δ(13)C-value. Thus, HT-RPLC/IRMS can be a very promising tool in stable isotope analysis of nonvolatile compounds.     

Uncertainty in quantum mechanics: faith or fantasy?

The word 'uncertainty', in the context of quantum mechanics, usually evokes an impression of an essential unknowability of what might actually be going on at the quantum level of activity, as is made explicit in Heisenberg's uncertainty principle, and in the fact that the theory normally provides only probabilities for the results of quantum measurement. These issues limit our ultimate understanding of the behaviour of things, if we take quantum mechanics to represent an absolute truth. But they do not cause us to put that very 'truth' into question. This article addresses the issue of quantum 'uncertainty' from a different perspective, raising the question of whether this term might be applied to the theory itself, despite its unrefuted huge success over an enormously diverse range of observed phenomena. There are, indeed, seeming internal contradictions in the theory that lead us to infer that a total faith in it at all levels of scale leads us to almost fantastical implications.     

Uncertainty in macroeconomic policy-making: art or science?

Uncertainty is pervasive in economic policy-making. Modern economies share similarities with other complex systems in their unpredictability. But economic systems also differ from those in the natural sciences because outcomes are affected by the state of beliefs of the systems' participants. The dynamics of beliefs and how they interact with economic outcomes can be rich and unpredictable. This paper relates these ideas to the recent crisis, which has reminded us that we need a financial system that is resilient in the face of the unpredictable and extreme. It also highlights how such uncertainty puts a premium on sound communication strategies by policy-makers. This creates challenges in informing others about the uncertainties in the economy, and how policy is set in the face of those uncertainties. We show how the Bank of England tries to deal with some of these challenges in its communications about monetary policy.     

Non-English journals and papers in physics and chemistry: bias in citations?

This study investigates, at the journal as well as the article level, if there is a difference in citations between English-language and non-English publications. The Web of Knowledge is used as data source. The investigation focuses on the fields of physics and chemistry. Using a precise definition of a “non-English journal”, we filter out nine physics and thirty-four chemistry non-English journals, scattered over six physics and seven chemistry subfields. Average received citations per paper (CpP) of the non-English journal(s) are compared with the CpP of pure English journals, and this in the same subfield. We clearly observe that non-English journals are inferior—in number of citations received—to pure English journals and this in all physics and chemistry subfields studied. Further, twelve physics journals and ten chemistry journals were chosen as sample journals to compare the CpP of non-English papers with that of English language papers in the same journal. The result of this comparison is that for the majority of these journals and for most of the publication years the CpP of non-English papers is lower than that of the English language papers. Finally, analyzing linguistic characteristics of the citing literature confirms the own-language preference in non-English physics and chemistry journals.     

The Application of ＂Risk = Value ＊ Threat ＊ Vulnerability＂ in Management Information Systems

With rapid development of the technology, many organizations depend more on the information than before and they will process mountains of information everyday. Hence, an information system is designed to facilitate managing information. Security is applied to insure data confidentiality, integrality and availability. In this process, risk can not be ignored. How can we analyze the degree of the risk we can accept to provide effective protection at reasonable costs with a great return on investment？ Now many methodologies are proposed. In the paper, one method ＂Risk = Value ＊ Threat ＊ Vulnerability＂ is analyzed so that more people can have a basic understanding about the risk.     

Grundlagenuntersuchung zu den Str?mungsverh?ltnissen in hochtourigen Turbinengleitlagern: Str?mung in einem Konfusor mit einseitig bewegter Berandung

The flow in a confusor with a plane moving wall was investigated both experimentally and numerically for a turbulent Reynolds-number of 9.95×10³. These fundamental results can be applied for journal bearings used in case of large turbo-machines. It is found that the moving wall (journal) leads to a turbulent boundary layer flow whereas the mean flow in the groove domains is turbulent with only weak secondary flow features like recirculation zones. By means of a comparison with LDA measurements it is shown that the Realizable k–ε-model is well suited for corresponding flow configurations.     

Gender differences in scientific productivity: a persisting phenomenon?

There is substantial literature on research performance differences between male and female researchers, and its explanation. Using publication records of 852 social scientists, we show that performance differences indeed exist. However, our case study suggests that in the younger generation of researchers these have disappeared. If performance differences exist at all in our case, young female researchers outperform young male researchers. The trend in developed societies, that women increasingly outperform men in all levels of education, is also becoming effective in the science system.     

Nonlinear instability in flagellar dynamics: a novel modulation mechanism in sperm migration?

Throughout biology, cells and organisms use flagella and cilia to propel fluid and achieve motility. The beating of these organelles, and the corresponding ability to sense, respond to and modulate this beat is central to many processes in health and disease. While the mechanics of flagellum–fluid interaction has been the subject of extensive mathematical studies, these models have been restricted to being geometrically linear or weakly nonlinear, despite the high curvatures observed physiologically. We study the effect of geometrical nonlinearity, focusing on the spermatozoon flagellum. For a wide range of physiologically relevant parameters, the nonlinear model predicts that flagellar compression by the internal forces initiates an effective buckling behaviour, leading to a symmetry-breaking bifurcation that causes profound and complicated changes in the waveform and swimming trajectory, as well as the breakdown of the linear theory. The emergent waveform also induces curved swimming in an otherwise symmetric system, with the swimming trajectory being sensitive to head shape—no signalling or asymmetric forces are required. We conclude that nonlinear models are essential in understanding the flagellar waveform in migratory human sperm; these models will also be invaluable in understanding motile flagella and cilia in other systems.     

Important Thermodynamic Parameters of Lithium–Tin Alloys from the Point of View of Their Use in Tokamaks

High Temperature - Along with other liquid metals, lithium–tin alloys are considered an alternative to the use of solid materials in the development of plasma-facing intrachamber components...