Understanding how excess lead iodide precursor improves halide perovskite solar cell performance

The presence of excess lead iodide in halide perovskites has been key for surpassing 20% photon-to-power conversion efficiency. To achieve even higher power conversion efficiencies, it is important to understand the role of remnant lead iodide in these perovskites. To that end, we explored the mechanism facilitating this effect by identifying the impact of excess lead iodide within the perovskite film on charge diffusion length, using electron-beam-induced current measurements, and on film formation properties, from grazing-incidence wide-angle X-ray scattering and high-resolution transmission electron microscopy. Based on our results, we propose that excess lead iodide in the perovskite precursors can reduce the halide vacancy concentration and lead to formation of azimuthal angle-oriented cubic alpha-perovskite crystals in-between 0 degrees and 90 degrees. We further identify a higher perovskite carrier concentration inside the nanostructured titanium dioxide layer than in the capping layer. These effects are consistent with enhanced lead iodide-rich perovskite solar cell performance and illustrate the role of lead iodide

Life cycle analysis and comparison of climate impact for two alternative floor systems for increased weight in high-rise timber buildings

The aim of this Master Thesis is to investigate and quantify the climate impact for two floor system alternatives for the Cederhusen project, that is the 8 floors timber-based buildings located at Sankt Eriksplan in Stockholm. The overall motivation for this study is the fact that the construction industry is a major contributor to the total amount of the global greenhouse gas emissions. Therefore, in order to reduce these emissions new solutions, practices and applications must be adopted. An environmental attentive choice of materials used in structures has the potential of reducing the emissions. The first alternative is the existing floor system solution used by Folkhem. The second is a new type of floor system solution patented by Granab. Each floor system contains two segments: a structural part and a sub-floor part. The structural part in both alternatives contain an adding weight component to improve the dynamic performance of the relatively light weight high-rise timber buidlings. Both floor systems are thus so-called hybrid systems, where Folkhem's solution combines cross-laminated timber (CLT) and steel fiber reinforced concrete, and Granab's solution combines CLT and gravel. The specific objective was to compare the emission of greenhouse gases related to each floor system and their components by a so-called comparative life cycle assessment (LCA) methodology using a well-defined functional unit. The functional unit must consider all significant performance requirements obtained by the floor system, including load bearing capacity, dynamic performance, sound proofing, fire safety, surface flooring and maximum acceptable building height. The method of determining the climate impact is based on the “Anavitor Concept”, an innovative and digital approach to LCA calculations, to quantify and compare the environmental impact of the two floor systems through their lifetime, aiming for the user to not be an LCA expert, but to be the one who develops the design solutions, called “End-User”. Therefore, this concept performs direct LCA calculations from the BIM model by allowing access to environmental database, which contains life cycle analysis data approved and provided by LCA environmental specialists, and conveniently link material component against an industry-wide resource register receipt, called “Cross-Referencing”. The results show a significant decrease of climate impact with 33 % CO2e/m2 for the Granab’s alternative floor system compared to the existing floor system designed by Folkhem. Moreover, a direct comparison of the climate impact of Folkhem´s versus Granab´s adding weight system itself, shows a remarkable decrease of climate impact with 65 % CO2e/m2 emissions reduction for the Granab system.  Thera are several reasons for these remarkably results, however, the building material selection of gravel over concrete has the greatest influence. In practice, the ability to avoid the environmental impact of cement’s manufacture process in the production stage, A1-A3, is identified as the hot spot of this study. In addition, the environmental impact results signify the importance of a wise selection of the manufacturer and their factory location, mainly by selecting a factory located as close as possible. However, in practice, there are also other factors which need to be considered when choosing a supplier. Moreover, allowing the user to not be an LCA expert but to be the one who develops the design solutions, based on the “End-User” idea in the “Anavitor Concept” applied in this study, has novel benefits. By implementing LCA analysis during the architectural and structural design process, additional quantified environmental results can be instantly considered as additional causal numerical factors in the design process and directly affect executive decisions in earlier design stages for environmental matter as well. “Anavitor Concept” is a game changer regarding LCA in the construction sector. A future where every consulting building company around the globe would have access to open verified regulated environmental database and simply with their BIM model would be able to receive immediate quantified and verified environmental impact outputs in the early stages of design by the designers themselves and not LCA expert consultant, is an environmental dream come true. The “Anavitor Concept” should be adopted and expend outside the Swedish market and the environmental database should be adapted and modified to each national construction market around the globe

Life cycle analysis and comparison of climate impact for two alternative floor systems for increased weight in high-rise timber buildings

The aim of this Master Thesis is to investigate and quantify the climate impact for two floor system alternatives for the Cederhusen project, that is the 8 floors timber-based buildings located at Sankt Eriksplan in Stockholm. The overall motivation for this study is the fact that the construction industry is a major contributor to the total amount of the global greenhouse gas emissions. Therefore, in order to reduce these emissions new solutions, practices and applications must be adopted. An environmental attentive choice of materials used in structures has the potential of reducing the emissions. The first alternative is the existing floor system solution used by Folkhem. The second is a new type of floor system solution patented by Granab. Each floor system contains two segments: a structural part and a sub-floor part. The structural part in both alternatives contain an adding weight component to improve the dynamic performance of the relatively light weight high-rise timber buidlings. Both floor systems are thus so-called hybrid systems, where Folkhem's solution combines cross-laminated timber (CLT) and steel fiber reinforced concrete, and Granab's solution combines CLT and gravel. The specific objective was to compare the emission of greenhouse gases related to each floor system and their components by a so-called comparative life cycle assessment (LCA) methodology using a well-defined functional unit. The functional unit must consider all significant performance requirements obtained by the floor system, including load bearing capacity, dynamic performance, sound proofing, fire safety, surface flooring and maximum acceptable building height. The method of determining the climate impact is based on the “Anavitor Concept”, an innovative and digital approach to LCA calculations, to quantify and compare the environmental impact of the two floor systems through their lifetime, aiming for the user to not be an LCA expert, but to be the one who develops the design solutions, called “End-User”. Therefore, this concept performs direct LCA calculations from the BIM model by allowing access to environmental database, which contains life cycle analysis data approved and provided by LCA environmental specialists, and conveniently link material component against an industry-wide resource register receipt, called “Cross-Referencing”. The results show a significant decrease of climate impact with 33 % CO2e/m2 for the Granab’s alternative floor system compared to the existing floor system designed by Folkhem. Moreover, a direct comparison of the climate impact of Folkhem´s versus Granab´s adding weight system itself, shows a remarkable decrease of climate impact with 65 % CO2e/m2 emissions reduction for the Granab system.  Thera are several reasons for these remarkably results, however, the building material selection of gravel over concrete has the greatest influence. In practice, the ability to avoid the environmental impact of cement’s manufacture process in the production stage, A1-A3, is identified as the hot spot of this study. In addition, the environmental impact results signify the importance of a wise selection of the manufacturer and their factory location, mainly by selecting a factory located as close as possible. However, in practice, there are also other factors which need to be considered when choosing a supplier. Moreover, allowing the user to not be an LCA expert but to be the one who develops the design solutions, based on the “End-User” idea in the “Anavitor Concept” applied in this study, has novel benefits. By implementing LCA analysis during the architectural and structural design process, additional quantified environmental results can be instantly considered as additional causal numerical factors in the design process and directly affect executive decisions in earlier design stages for environmental matter as well. “Anavitor Concept” is a game changer regarding LCA in the construction sector. A future where every consulting building company around the globe would have access to open verified regulated environmental database and simply with their BIM model would be able to receive immediate quantified and verified environmental impact outputs in the early stages of design by the designers themselves and not LCA expert consultant, is an environmental dream come true. The “Anavitor Concept” should be adopted and expend outside the Swedish market and the environmental database should be adapted and modified to each national construction market around the globe

The Prevalence of Temporomandibular Disorders and Dental Attrition Levels in Patients with Posterior Crossbite and/or Deep Bite: A Preliminary Prospective Study

Background. The prevalence of various temporomandibular disorders (TMD) and the severity of attrition in patients with either bilateral or unilateral deep bite and/or posterior crossbite has not been established, nor has the effect of one year of orthodontic treatment on TMD. Methods. Of 310 patients presenting with suspected TMD, 160 were diagnosed with various TMD and 150 were TMD-free. Diagnosis was according to the Axis I of the Diagnostic Criteria for TMD. All participants underwent a dental examination, and 100 patients were reevaluated after one year of orthodontic treatment. Fisher’s exact test and the proportion test with Bonferroni’s correction were used for the categorical univariate analysis. Results. There was a significant association (P<0.001) between deep bite and dental attrition (wear), but not between crossbite and/or deep bite in patients diagnosed with either painful TMD or disc displacement. The risk of sustaining painful TMD when crossbite presented simultaneously on the anterior and the posterior dentition was 2.625-fold greater than when it presented with a normal bite, although this difference was not significant (P=0.286) due to the lack of statistical power. There was no significant sex-related association between the occurrence of either painful TMD or disc displacement. A reduction in TMD findings was demonstrated after one year of treatment, but no statistical power was reached due to the small sample size. Conclusions. Deep bite may be related to dental wear but not to pain from TMD and/or disc displacement. Only crossbite that presents simultaneously on the anterior and the posterior dentition (mixed X-bite) may have some effect on the level of pain in TMD, but not on in the prevalence of disc displacement. Confirmation of these conclusions by well-designed studies on larger patient groups is warranted. There was a clinically significant improvement in TMD findings after one year of treatment

Arrangements of Segments that Share Endpoints: Single Face Results

We provide new combinatorial bounds on the complexity of a face in an arrangement of segments in the plane. In particular, we show that the complexity of a single face in an arrangement of n line segments determined by h endpoints is O(h log h). While the previous upper bound, O(nff(n)), is tight for segments with distinct endpoints, it is far from being optimal when n = \Omega\Gamma h 2 ). Our result shows that, in a sense, the fundamental combinatorial complexity of a face arises not as a result of the number of segments, but rather as a result of the number of endpoints. 1 Introduction Let S = fs 1 ; : : : ; s n g be a finite set of n line segments in the plane. Then S induces a partition of the plane, called the arrangement A(S) of S, into O(n 2 ) faces, edges and vertices. Refer to Figure 1. Arrangements of segments play a fundamental role in computational geometry (see, e.g., [EGS]). The problem studied here is that in which the segments S are allowed to share endpoints, so ..

Higher Open Circuit Voltage and Reduced UV-Induced Reverse Current in ZnO-Based Solar Cells by a Chemically Modified Blocking Layer

Solid-state semiconductor-sensitized solar cells require a thin, dense hole-blocking layer at the conducting glass substrate (F-doped tin oxide (FTO)) to prevent shorting beween the FTO and hole conductor. We found that by adding a small amount of Sb ions to a ZnO chemical deposition bath a thin (few tens of nanometers thick) dense and uniform layer of Sb-incorporated ZnO forms. Here we investigate the electronic properties of this layer in comparison to the continuous ZnO layer at the base of the ZnO rods formed in the standard preparation. Devices incorporating the Sb-incorporated dense layer followed by a standard ZnO nanorod growth, onto which CdS or CdSe was grown followed by a CuSCN hole conductor, showed 100–200 mV higher photovoltage together with occasional improvement in the short-circuit current. Electrochemical and electrical measurements indicated complete coverage of the FTO substrate by both preparations; however, the shunt resistance (resistance to a reverse leakage current) in the cells (and films) made using the Sb-incorporated ZnO layer is dramatically increased. Using bias-dependent incident photon-to-electron conversion efficiency studies, we found that an increased dark or leakage current develops in the cell on illumination with UV light together with application of a forward bias. This can be explained by the presence of a “Schottky junction” at the FTO\ZnO interface. This increased leakage current is significantly larger in cells without the Sb-incorporated ZnO compact layer