Formamidinium-lead-iodide (FAPbI3)-based perovskites with bandgap below 1.55 eV are of interest for photovoltaics in view of their close-to-ideal bandgap. Record-performance FAPbI3-based solar cells have relied on fabrication via the sequential-deposition method; however, these devices exhibit unstable output under illumination due to the difficulty of incorporating cesium cations (stabilizer) in sequentially deposited films. Here we devise a perovskite seeding method that efficiently incorporates cesium and beneficially modulates perovskite crystallization. First, perovskite seed crystals are embedded in the PbI2 film. The perovskite seeds serve as cesium sources and act as nuclei to facilitate crystallization during the formation of perovskite. Perovskite films with perovskite seeding growth exhibit a lowered trap density, and the resulting planar solar cells achieve stabilized efficiency of 21.5% with a high open-circuit voltage of 1.13 V and a fill factor that exceeds 80%. The Cs-containing FAPbI3-based devices show a striking improvement in operational stability and retain 60% of their initial efficiency after 140 h operation under one sun illumination.

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Copper-based materials are promising electrocatalysts for CO2 reduction. Prior studies show that the mixture of copper (I) and copper (0) at the catalyst surface enhances multi-carbon products from CO2 reduction; however, the stable presence of copper (I) remains the subject of debate. Here we report a copper on copper (I) composite that stabilizes copper (I) during CO2 reduction through the use of copper nitride as an underlying copper (I) species. We synthesize a copper-on-nitride catalyst that exhibits a Faradaic efficiency of 64 ± 2% for C2+ products. We achieve a 40-fold enhancement in the ratio of C2+ to the competing CH4 compared to the case of pure copper. We further show that the copper-on-nitride catalyst performs stable CO2 reduction over 30 h. Mechanistic studies suggest that the use of copper nitride contributes to reducing the CO dimerization energy barrier—a rate-limiting step in CO2 reduction to multi-carbon products.

Impressive progress in halide perovskite solar cells motivates further work to improve operating stability. It is known that ion-migration-driven decomposition represents a degradation pathway in perovskite solar cells and that it can occur within the perovskite material even in well-encapsulated devices. Here we find that quasi-two-dimensional (2.5D) perovskites suppress this ionmigration-induced degradation. Using TOF-SIMS, we confirm that iodide migration occurs in bulk perovskite photovoltaic devices operating at their maximum power point (MPP). We observe that iodine ions migrate across the spiro-OMeTAD layer to the spiro/ gold contact interface, oxidizing and deteriorating the gold at the interface. In contrast, we find that large ⟨n⟩ 2.5D perovskites exhibit a significantly reduced rate of ion migration compared to 3D devices and exhibit less than 1% relative PCE loss in over 80 h of continuous operation at MPP, whereas the PCE of 3D devices diminishes by more than 50% within the first 24 h.

Organic–inorganic hybrid perovskite solar cells (PSCs) have seen a rapid rise in power conversion efficiencies in recent years; however, they still suffer from interfacial recombination and charge extraction losses at interfaces between the perovskite absorber and the charge–transport layers. Here, in situ back‐contact passivation (BCP) that reduces interfacial and extraction losses between the perovskite absorber and the hole transport layer (HTL) is reported. A thin layer of nondoped semiconducting polymer at the perovskite/HTL interface is introduced and it is shown that the use of the semiconductor polymer permits—in contrast with previously studied insulator‐based passivants—the use of a relatively thick passivating layer. It is shown that a flat‐band alignment between the perovskite and polymer passivation layers achieves a high photovoltage and fill factor: the resultant BCP enables a photovoltage of 1.15 V and a fill factor of 83% in 1.53 eV bandgap PSCs, leading to an efficiency of 21.6% in planar solar cells.

BackgroundGovernment interventions are critical to addressing the global tobacco epidemic, a major public health problem that continues to deepen. We systematically synthesize research evidence on the effectiveness of government tobacco control policies promoted by the Framework Convention on Tobacco Control (FCTC), supporting the implementation of this international treaty on the tenth anniversary of it entering into force.MethodsAn overview of systematic reviews was prepared through systematic searches of five electronic databases, published up to March 2014. Additional reviews were retrieved from monthly updates until August 2014, consultations with tobacco control experts and a targeted search for reviews on mass media interventions. Reviews were assessed according to predefined inclusion criteria, and ratings of methodological quality were either extracted from source databases or independently scored.ResultsOf 612 reviews retrieved, 45 reviews met the inclusion criteria and 14 more were identified from monthly updates, expert consultations and a targeted search, resulting in 59 included reviews summarizing over 1150 primary studies. The 38 strong and moderate quality reviews published since 2000 were prioritized in the qualitative synthesis. Protecting people from tobacco smoke was the most strongly supported government intervention, with smoke-free policies associated with decreased smoking behaviour, secondhand smoke exposure and adverse health outcomes. Raising taxes on tobacco products also consistently demonstrated reductions in smoking behaviour. Tobacco product packaging interventions and anti-tobacco mass media campaigns may decrease smoking behaviour, with the latter likely an important part of larger multicomponent programs. Financial interventions for smoking cessation are most effective when targeted at smokers to reduce the cost of cessation products, but incentivizing quitting may be effective as well. Although the findings for bans on tobacco advertising were inconclusive, other evidence suggests they remain an important intervention.ConclusionWhen designing and implementing tobacco control programs, governments should prioritize smoking bans and price increases of tobacco products followed by other interventions. Additional studies are needed on the various factors that can influence a policy’s effectiveness and feasibility such as cost, local context, political barriers and implementation strategies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12889-015-2041-6) contains supplementary material, which is available to authorized users.

BackgroundCelebrities can have substantial influence as medical advisors. However, their impact on public health is equivocal: depending on the advice’s validity and applicability, celebrity engagements can benefit or hinder efforts to educate patients on evidence-based practices and improve their health literacy. This meta-narrative analysis synthesizes multiple disciplinary insights explaining the influence celebrities have on people’s health-related behaviors.MethodsSystematic searches of electronic databases BusinessSource Complete, Communication & Mass Media Complete, Humanities Abstracts, ProQuest Political Science, PsycINFO, PubMed, and Sociology Abstracts were conducted. Retrieved articles were used to inform a conceptual analysis of the possible processes accounting for the substantial influence celebrities may have as medical advisors.ResultsFourteen mechanisms of celebrity influence were identified. According to the economics literature, celebrities distinguish endorsed items from competitors and can catalyze herd behavior. Marketing studies tell us that celebrities’ characteristics are transferred to endorsed products, and that the most successful celebrity advisors are those viewed as credible, a perception they can create with their success. Neuroscience research supports these explanations, finding that celebrity endorsements activate brain regions involved in making positive associations, building trust and encoding memories. The psychology literature tells us that celebrity advice conditions people to react positively toward it. People are also inclined to follow celebrities if the advice matches their self-conceptions or if not following it would generate cognitive dissonance. Sociology explains how celebrities’ advice spreads through social networks, how their influence is a manifestation of people’s desire to acquire celebrities’ social capital, and how they affect the ways people acquire and interpret health information.ConclusionThere are clear and deeply rooted biological, psychological and social processes that explain how celebrities influence people’s health behaviors. With a better understanding of this phenomenon, medical professionals can work to ensure that it is harnessed for good rather than abused for harm. Physicians can discuss with their patients the validity of celebrity advice and share more credible sources of health information. Public health practitioners can debunk celebrities offering unsubstantiated advice or receiving inappropriate financial compensation, and should collaborate with well-meaning celebrities, leveraging their influence to disseminate medical practices of demonstrated benefit.Electronic supplementary materialThe online version of this article (doi:10.1186/2049-3258-73-3) contains supplementary material, which is available to authorized users.

When considered together, the traditional 'red flags' for NF may be sufficient to rule in or rule out the diagnosis. If future prospective studies validate these findings, there will be a potential opportunity to expedite NF diagnosis and improve patient outcomes.