Infiltration issues in printed mesoporous carbon perovskite solar cells: a troubleshooting guide

Printed mesoscopic carbon perovskite solar cells (CPSCs) represent a potential frontrunner to perovskite commercialisation due to their inherent stability and easily scaled fabrication methods. Devices consist of three screen printed mesoporous layers of TiO2, ZrO2 and carbon, which are subsequently infiltrated with perovskite. It is well established that complete infiltration, or filling, of the base TiO2 layer is key to achieving peak performance and reproducibility in both lab-scale devices and modules. A thorough understanding of the factors influencing infiltration is therefore essential for both lab-scale research and scale-up. TiO2 infiltration is easily examined by optical microscopy through the glass substrate. This work identifies common characteristic infiltration defects at multiple scales, caused by specific issues in the manufacturing process such as mesh marking, printing issues, contaminant damage and environmental fluctuations. Likely causes and potential solutions are presented for each type of defect, to produce a troubleshooting reference resource for tackling this problem at multiple scales. This should help enhance lab-scale reproducibility providing a simple method for quality control in future large-scale ventures

Scribing Method for Carbon Perovskite Solar Modules

The fully printable carbon triple-mesoscopic perovskite solar cell (C-PSC) has already demonstrated good efficiency and long-term stability, opening the possibility of lab-to-fab transition. Modules based on C-PSC architecture have been reported and, at present, are achieved through the accurate registration of each of the patterned layers using screen-printing. Modules based on this approach were reported with geometric fill factor (g-FF) as high as 70%. Another approach to create the interconnects, the so-called scribing method, was reported to achieve more than 90% g-FF for architectures based on evaporated metal contacts, i.e., without a carbon counter electrode. Here, for the first time, we adopt the scribing method to selectively remove materials within a C-PSC. This approach allowed a deep and selective scribe to open an aperture from the transparent electrode through all the layers, including the blocking layer, enabling a direct contact between the electrodes in the interconnects. In this work, a systematic study of the interconnection area between cells is discussed, showing the key role of the FTO/carbon contact. Furthermore, a module on 10 × 10 cm2 substrate with the optimised design showing efficiency over 10% is also demonstrated

Evolutions of the Reference Values Used in Transport CBA National Guidelines of 3 Countries and What they Reveal

The paper presents, analyses and compares the evolution of reference values used in national guidelines issued for cost-benefit analysis of transport infrastructure projects, over the last fifty years, in France, UK and Germany

In situ monitoring of corrosion mechanisms and phosphate inhibitor surface deposition during corrosion of zinc–magnesium–aluminium (ZMA) alloys using novel time-lapse microscopy

In-situ time-lapse optical microscopy was used to examine the microstructural corrosion mechanisms in three zinc-magnesium-aluminium (ZMA) alloy coated steels immersed in 1% NaCl pH 7. Preferential corrosion of MgZn2 lamellae within the eutectic phases was observed in all the ZMA alloys followed by subsequent dissolution of Zn rich phases. The total extent and rate of corrosion, measured using time-lapse image analysis and scanning vibrating electrode technique (SVET) estimated mass loss, decreased as Mg and Al alloying additions were increased up to a level of 3 wt% Mg and 3.7 wt% Al. This was probably due to the increased presence of MgO and Al2O3 at the alloy surface retarding the kinetics of cathodic oxygen reduction. The addition of 1 x 10-2 mol/dm3 Na3PO4 to 1% NaCl pH 7 had a dramatic influence on the corrosion mechanism for a ZMA with passivation of anodic sites through phosphate precipitation observed using time-lapse. Intriguing rapid precipitation of filamentous phosphate was also observed and it is postulated that these filaments nucleate and grow due to super saturation effects. Polarisation experiments showed that the addition of 1 x 10-2 mol/dm3 Na3PO4 to the 1% NaCl electrolyte promoted an anodic shift of 50mV in open circuit potential for the ZMA alloy with a reduction in anodic current of 2.5 orders of magnitude suggesting that it was acting primarily as an anodic inhibitor supporting the inferences from the time-lapse investigations. These phosphate additions resulted in a 98% reduction in estimated mass loss as measured by SVET demonstrating the effectiveness of phosphate inhibitors for this alloy system

The contribution of AGN to the sub-mm population

We find that X-ray sources in the Extended Chandra Deep Field South are strongly spatially correlated with LABOCA 870 micron sources. We investigate the dependence of this correlation on X-ray flux, hardness ratio and column density, finding that specifically faint and absorbed X-ray sources are significant sub-mm emitters. In the X-ray source redshift subsample we confirm the previous result that higher luminosity sources (L_X>10^44 ergs/s) have greater 870um fluxes but we also find that this subsample selects against absorbed sources, faint in X-ray flux. Overall, we find that X-ray sources contribute 1.5 \pm 0.1 Jy/deg^2 to the sub-mm background, ~3% of the total, in agreement with the prediction of an obscured AGN model which also gives a reasonable fit to the bright sub-mm source counts. This non-unified model also suggests that when Compton-thick, X-ray-undetected sources are included, then the fractional AGN contribution to the sub-mm background would rise from ~3% to a total of 25-40%, although in a unified model the AGN contribution would only reach ~13%, because the sub-mm flux of the X-ray sources is then more representative of the whole AGN population. Measurements of the dependence of sub-mm flux on X-ray flux, luminosity and column density all agree well with the predictions of the non-unified AGN model. Heavily absorbed, X-ray-undetected AGN could explain the further cross-correlation we find between sub-mm sources and z > 0.5 red galaxies. We conclude that sub-mm galaxies may contain the long-sought absorbed AGN population needed to explain the X-ray background.Comment: 15 pages, 13 figures; submitted to MNRA

Transport appraisal revisited

Cost-benefit analysis has become a widely used and well developed tool for evaluation of suggested transport projects. This paper presents our view of the role and position of CBA in a transport planning process, partly based on a survey of a number of countries where CBA plays a formalised role in decision making. The survey shows that methodologies, valuations and areas of application are broadly similar across countries. All countries place the CBA results in a comprehensive assessment framework that also includes various types of non-monetised benefits. An important advantage with using CBA is that it is a way to overcome cognitive, structural and process-related limitations and biases in decision making. Some of the main challenges to CBA and to quantitative assessment in general lie in the institutional and political context. There is often a risk that CBA enters the planning process too late to play any meaningful role. This risk seems to increase when planning processes are centred around a perceived "problem". If the problem is perceived as important enough, even inefficient solutions may be viewed as better than nothing, despite that the definition of what constitutes a "problem" is often arbitrary

New appraisal values of travel time saving and reliability in Great Britain

© 2017, The Author(s). This paper provides an overview of the study ‘Provision of market research for value of time savings and reliability’ undertaken by the Arup/ITS Leeds/Accent consortium for the UK Department for Transport (DfT). The paper summarises recommendations for revised national average values of in-vehicle travel time savings, reliability and time-related quality (e.g. crowding and congestion), which were developed using willingness-to-pay (WTP) methods, for a range of modes, and covering both business and non-work travel purposes. The paper examines variation in these values by characteristics of the traveller and trip, and offers insights into the uncertainties around the values, especially through the calculation of confidence intervals. With regards to non-work, our recommendations entail an increase of around 50% in values for commute, but a reduction of around 25% for other non-work—relative to previous DfT ‘WebTAG’ guidance. With regards to business, our recommendations are based on WTP, and thus represent a methodological shift away from the cost saving approach (CSA) traditionally used in WebTAG. These WTP-based business values show marked variation by distance; for trips of less than 20miles, values are around 75% lower than previous WebTAG values; for trips of around 100miles, WTP-based values are comparable to previous WebTAG; and for longer trips still, WTP-based values exceed those previously in WebTAG

Can Sophie's Choice Be Adequately Captured by Cold Computation of Minimizing Losses? An fMRI Study of Vital Loss Decisions

The vast majority of decision-making research is performed under the assumption of the value maximizing principle. This principle implies that when making decisions, individuals try to optimize outcomes on the basis of cold mathematical equations. However, decisions are emotion-laden rather than cool and analytic when they tap into life-threatening considerations. Using functional magnetic resonance imaging (fMRI), this study investigated the neural mechanisms underlying vital loss decisions. Participants were asked to make a forced choice between two losses across three conditions: both losses are trivial (trivial-trivial), both losses are vital (vital-vital), or one loss is trivial and the other is vital (vital-trivial). Our results revealed that the amygdala was more active and correlated positively with self-reported negative emotion associated with choice during vital-vital loss decisions, when compared to trivial-trivial loss decisions. The rostral anterior cingulate cortex was also more active and correlated positively with self-reported difficulty of choice during vital-vital loss decisions. Compared to the activity observed during trivial-trivial loss decisions, the orbitofrontal cortex and ventral striatum were more active and correlated positively with self-reported positive emotion of choice during vital-trivial loss decisions. Our findings suggest that vital loss decisions involve emotions and cannot be adequately captured by cold computation of minimizing losses. This research will shed light on how people make vital loss decisions

Populism, ideology and contradiction: mapping young people's political views

Forms of populism have long been a component of modern political discourse and systems where democracy relies upon popular legitimacy. There is, however, an uneasy relationship between some widely held views of ‘the people’ and the parties which seek to govern them. Contemporary academic and political discourse on populism often equates these views with right-wing politics, whilst some radical scholars, suggest that these views, whilst controversial, are nonetheless examples of democratic expression. Using survey evidence from 14 European countries, we show that young people take up a mixture of political positions, some of which are strongly associated with indices of populism – cynicism, authoritarianism, nativism, xenophobia – others of which do not map neatly onto the typical ‘left-right’ spectrum. We find evidence that some young people hold contradictory, often conflicting political viewpoints, which are reflective of the historical and cultural contexts of each location rather than of a ‘populist’ ideology. Where some theorists might use the term ‘populism’ pejoratively to denote a poorly and emotively grounded political ideology, we argue that this description denies its democratic legitimacy, as evidence suggests that young people draw on populist rhetoric to articulate views that are more reflective of local and regional concerns