Author Correction: Maximizing and stabilizing luminescence from halide perovskites with potassium passivation.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Maximizing and stabilizing luminescence from halide perovskites with potassium passivation.

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield-a quantity that must be maximized to obtain high efficiency-remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

Formation of Long-Lived Color Centers for Broadband Visible Light Emission in Low-Dimensional Layered Perovskites.

We investigate the origin of the broadband visible emission in layered hybrid lead-halide perovskites and its connection with structural and photophysical properties. We study ⟨001⟩ oriented thin films of hexylammonium (HA) lead iodide, (C6H16N)2PbI4, and dodecylammonium (DA) lead iodide, (C12H28N)2PbI4, by combining first-principles simulations with time-resolved photoluminescence, steady-state absorption and X-ray diffraction measurements on cooling from 300 to 4 K. Ultrafast transient absorption and photoluminescence measurements are used to track the formation and recombination of emissive states. In addition to the excitonic photoluminescence near the absorption edge, we find a red-shifted, broadband (full-width at half-maximum of about 0.4 eV), emission band below 200 K, similar to emission from ⟨110⟩ oriented bromide 2D perovskites at room temperature. The lifetime of this sub-band-gap emission exceeds that of the excitonic transition by orders of magnitude. We use X-ray diffraction measurements to study the changes in crystal lattice with temperature. We report changes in the octahedral tilt and lattice spacing in both materials, together with a phase change around 200 K in DA2PbI4. DFT simulations of the HA2PbI4 crystal structure indicate that the low-energy emission is due to interstitial iodide and related Frenkel defects. Our results demonstrate that white-light emission is not limited to ⟨110⟩ oriented bromide 2D perovskites but a general property of this class of system, and highlight the importance of defect control for the formation of low-energy emissive sites, which can provide a pathway to design tailored white-light emitters.

The role of dynamic measurements in correlating structure with optoelectronic properties in polymer : fullerene bulk-heterojunction solar cells.

The characterization of morphology in blend thin-films of conjugated polymers and functionalized fullerenes is a critical aspect in organic photovoltaic (OPV) device research. Understanding the links between thin-film processing conditions, film nanostructure and photocurrent generation efficiency is necessary in order to develop this technology for commercial viability. Here, we review recent developments of experimental studies that probe sample nanostructure formation and modification during the processing steps commonly used in OPV device fabrication, potentially offering a deeper insight and more rational understating of these conditions.

Fluorene-based co-polymer with high hole mobility and device performance in bulk heterojunction organic solar cells.

A new donor-acceptor polymer based on 9,9-dioctylfluorene is synthesized and tested in organic photovoltaic devices. Results show that the polymer exhibits good solubility in a range of organic solvents and has a high hole mobility. When blended with a PC70 BM acceptor and fabricated into a bulk heterojunction, photovoltaic devices having a maximum power conversion efficiency (PCE) of 6.2% and a peak external quantum efficiency of 74% are created. Such efficiencies are realized without any necessity for solvent additives or thermal annealing protocols.

Changing incentives to ACCELERATE drug development for paediatric cancer.

BACKGROUND: More effective incentives are needed to motivate paediatric oncology drug development, uncoupling it from dependency on adult drug development. Although the current European and North-American legislations aim to promote drug development for paediatrics and rare diseases, children and adolescents with cancer have not benefited as expected from these initiatives and cancer remains the first cause of death by disease in children older than one. Drug development for childhood cancer remains dependent on adult cancer indications and their potential market. The balance between the investment needed to execute a Paediatric Investigation Plan (PIP) in Europe and an initial Paediatric Study Plan (iPSP) in the US, coupled with the potential financial reward has not been sufficiently attractive to incite the pharmaceutical industry to develop drugs for rare indications such as childhood cancer. METHODS: We propose changes in the timing and nature of the rewards within the European Paediatric Medicine Regulation (PMR) and Regulation on Orphan Medicinal Products (both currently under review), which would drive earlier initiation of paediatric oncology studies and provide incentives for drug development specifically for childhood indications. RESULTS: We suggest modifying the PMR to ensure mechanism-of-action driven mandatory PIP and reorganization of incentives to a stepwise and incremental approach. Interim and final deliverables should be defined within a PIP or iPSP, each attracting a reward on completion. A crucial change would be the introduction of the interim deliverable requiring production of paediatric data that inform the go/no-go decisions on whether to take a drug forward to paediatric efficacy trials. CONCLUSION: Additionally, to address the critical gap in the current framework where there is a complete lack of incentives to promote paediatric-specific cancer drug development, we propose the introduction of early rewards in the Orphan Regulation, with a variant on the US-Creating Hope Act and its priority review vouchers.

Competition between substrate-mediated π-π stacking and surface-mediated T(g) depression in ultrathin conjugated polymer films.

We report surface and interface effects in dynamics and chain conformation in the thin film of conjugated polymer PCDTBT. To probe dynamic anomalies, we measure the glass transition temperature (T(g)) of PCDTBT films as a function of thickness, and find that there is a significant depression in T(g) for films less than 100 nm thick; a result qualitatively similar to that observed in many other polymer film systems. However, for films less than 40 nm, the T(g) converges to a constant value of 20 K below its bulk value. Grazing incidence X-ray diffraction shows depth-dependent molecular organization that is associated with the unusual thickness-dependent dynamics.

Imaging the bulk nanoscale morphology of organic solar cell blends using helium ion microscopy.

We use helium ion microscopy (HeIM) to image the nanostructure of poly(3-hexylthiophene)/[6,6]-phenyl-C(61)-butric acid methyl ester (P3HT/PCBM) blend thin-films. Specifically, we study a blend thin-film subject to a thermal anneal at 140 °C and use a plasma-etching technique to gain access to the bulk of the blend thin-films. We observe a domain structure within the bulk of the film that is not apparent at the film-surface and tentatively identify a network of slightly elongated PCBM domains having a spatial periodicity of (20 ± 4) nm a length of (12 ± 8) nm.

Dose assessment for polonium-210 (Po-210) in New Zealand shellfish.

Worldwide, Po-210 is an important contributor to human ionising radiation exposure through food. To characterise the ionising radiation dose for New Zealanders from Po-210 in shellfish, a dose assessment was undertaken. Deterministic and probabilistic dietary models were constructed by assigning shellfish consumption rates to Po-210 activity concentrations measured in shellfish. Modelling was undertaken for different shellfish consumer populations and geographical areas. Dietary modelling estimated an annual dose range from 4 µSv to 6070 µSv. The lowest dose was calculated for the overall shellfish consumer population residing in areas where baseline Po-210 activity concentrations were measured in shellfish. The highest dose was calculated for the high shellfish consumer population residing in areas where elevated activity concentrations were measured in shellfish. For the majority of the New Zealand population, the total estimated dose did not exceed the selected reference level of 1000 µSv, and Po-210 is therefore not a cause of concern. About 50% of high shellfish consumers residing in areas where shellfish had elevated Po-210 activity concentrations were exposed to ionising radiation resulting in an annual dose higher than 1000 µSv. Exposure assessment for different demographic groups identified that higher shellfish consumption rates in the population identifying as Maori lead to higher doses of ionising radiation for this group.

Radium in New Zealand agricultural soils: Crop uptake and estimation of current and future ionising radiation dose.

Crop uptake of 226Ra over a range of key New Zealand agricultural and horticultural growing areas was analysed to establish the dietary implications of an increase in soil 226Ra activity concentrations. Thirty crop samples, covering both feed and food commodities, were quantified for 226Ra activity concentrations, and concentration ratio (CRs) from the soil activity were calculated. The calculated CRs correlated with international default values for estimating crop uptake. Variation in CRs established that there was no increase in the crop activity concentration, relative to soil 226Ra from pasture foliage at a fertiliser impacted site, with a gradient of soil 226Ra activity concentrations. Based on the calculated CRs, the upper bound of the theoretical range of dietary exposures to 226Ra was 78.1 µSv/yr for teenage boys. Future forecasting of the increased dietary dose of 226Ra that might occur at the current soil loading rate, based on current fertiliser activity concentrations, confirmed that long-term loading of soil with 226Ra is unlikely to present a dietary risk. The forecast model calculated that the increase in dietary ionising radiation burden is unlikely to reach thresholds requiring regulatory intervention for two millennia.

Characterization and Lifetime Dietary Risk Assessment of Eighteen Pyrrolizidine Alkaloids and Pyrrolizidine Alkaloid N-Oxides in New Zealand Honey.

Pyrrolizidine alkaloids (PAs) are a large group of botanical toxins of concern, as they are considered genotoxic carcinogens, with long-term dietary exposure presenting an elevated risk of liver cancer. PAs can contaminate honey through honeybees visiting the flowers of PA-containing plant species. A program of monitoring New Zealand honey has been undertaken over several years to build a comprehensive dataset on the concentration, regional and seasonal distribution, and botanical origin of 18 PAs and PA N-oxides. A bespoke probabilistic exposure model has then been used to assess the averaged lifetime dietary risk to honey consumers, with exposures at each percentile of the model characterized for risk using a margin of exposure from the Joint World Health Organization and United Nations Food and Agriculture Organization Expert Committee on Food Additives (JECFA) Benchmark Dose. Survey findings identify the typical PA types for New Zealand honey as lycopsamine, echimidine, retrorsine and senecionine. Regional and seasonal variation is evident in the types and levels of total PAs, linked to the ranges and flowering times of certain plants. Over a lifetime basis, the average exposure an individual will receive through honey consumption is considered within tolerable levels, although there are uncertainties over high and brand-loyal consumers, and other dietary contributors. An average lifetime risk to the general population from PAs in honey is not expected. However, given the uncertainties in the assessment, risk management approaches to limit or reduce exposures through honey are still of value.

Intercontinental collaboration in clinical trials for children and adolescents with cancer-A systematic review by ACCELERATE.

BACKGROUND: Since pediatric cancer drug development is a global enterprise, we sought to provide an overview of the landscape of intercontinental clinical trials in pediatric oncology opened over the last decade. METHODS: ClinicalTrials.gov was systematically searched to identify all clinical therapeutic trials which opened between 2010 and 2020 and recruited pediatric patients (<18 years) with cancer. RESULTS: Over the last 10 years, 295 (8.7%) of 3383 therapeutic pediatric cancer trials were international and 182 (5.4%) were intercontinental. Most intercontinental trials were phase-1 or 2, with 25% late-phase, 65% were sponsored by industry, and North America was involved in 92%. Industry-sponsored proportionally more phase-1 trials than academia (41% vs. 25%); conversely, academia sponsored more phase-2 and late-phase trials (39% and 31% vs. 36% and 21%, respectively) (p = 0.020). North America-Europe collaboration was predominantly industry sponsored as opposed to North America-Oceania and Europe-Oceania collaboration, more frequently academic (p < 0.0001). Most late-phase trials (18/20, 90%) focusing on pediatric malignancies were conducted by academic sponsors and 10 of these were conducted by Children's Oncology Group (COG)/National Cancer Institute in the United States and Oceania. There was no significant increase over time of intercontinental trials and a trend for a reduction in academic trials. CONCLUSIONS: Despite the relative rarity of childhood malignancies, especially within molecular subtypes, only 5.4% of pediatric cancer trials were intercontinental. The number of intercontinental trials remains small, with no significant increase over the last decade. The ACCELERATE International Collaboration Working Group aims to identify existing hurdles and propose solutions to improve intercontinental collaboration in clinical research for the benefit of children and adolescents with cancer.

Repeated unpredictable stress and social isolation induce chronic HPA axis dysfunction and persistent abnormal fear memory.

The lack of progress in the psychopharmacological treatment of stress-related disorders such as PTSD is an ongoing crisis due to its negative socioeconomic implications. Current PTSD pharmacotherapy relies on a few FDA approved medications used primarily for depression which offer only symptomatic relief and show limited efficacy. As the population of PTSD patients is growing, the identification of effective etiology-based treatments for the condition is a high priority. This requires an in-depth understanding of the neurobiological and behavioral outcomes of stress in translationally relevant animal models. In this study, we use neuroendocrine, biochemical and behavioral measures to assess the HPA axis function and fear-memory deficits in a mouse model of chronic stress. The chronic stress procedures involved exposure to 21 days of repeated unpredictable stress (RUS), including predator stress, restraint and foot shock, followed by chronic social isolation. We show that mice exposed to our stress paradigm demonstrate exaggerated fear memory recall and blunted HPA axis functionality at one month after RUS. Our neuroendocrinal testing suggests that the attenuated stress response in our model may be related to an alteration in the adrenal MC2 receptor reactivity. While there was no noticeable change in pituitary negative feedback regulation mechanisms, CRH and phosphorylated Glucocorticoid receptors levels were altered in the hypothalamus. We also show that chronic supplementation with a peripheral glucocorticoid receptor agonist (low-dose dexamethasone) after RUS partially restores a number of stress-related behavioral deficits in the RUS model. This suggests a direct relationship between HPA axis function and behavior in our model. Our findings emphasize the importance of the adrenal receptors as a target for HPA axis dysfunction in stress and fear-related disorders.

Risk assessment of antimony, barium, beryllium, boron, bromine, lithium, nickel, strontium, thallium and uranium concentrations in the New Zealand diet.

Identifying and monitoring dietary toxicants is an important component of contemporary food safety systems. To characterise their potential dietary risks, analysis was undertaken of 10 elements: antimony, barium, beryllium, boron, bromine, lithium, nickel, strontium, thallium and uranium in 132 different food types. All 10 elements were reported as quantified in aportion of the analysed foods, with prevalence ranging from less than 1% for antimony to 98% for barium. Dietary exposure assessment was undertaken for 10 New Zealand population cohorts using apublished simulated diet, and proportionality of food groups to total exposure identified. Characterisation against health-based guidance values identified no dietary risk from exposures to beryllium, boron, bromine, lithium, strontium and uranium to any of the population cohorts. For antimony and thallium, the exposure range for infants was calculated to exceed the health-based guidance value, and for barium and nickel, all mean exposures were above the health-based guidance value for younger population cohorts. Although some conservatism in applying upper-bound mean exposures reduces the likelihood of asignificant dietary risk, further laboratory method development and analysis of these elements in the New Zealand diet would be beneficial to ensure protection of New Zealand public health.

Mercury, methylmercury and long-chain polyunsaturated fatty acids in selected fish species and comparison of approaches to risk-benefit analysis.

Fish (n = 281) of six species, caught in New Zealand waters, were analysed for total mercury (t-Hg), methylmercury (MeHg) and the long-chain polyunsaturated fatty acids, eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA). Mean t-Hg and MeHg concentrations for the six species were in the range 0.06-0.53 mg/kg and 0.06-0.46 mg/kg, respectively. The mean proportion of t-Hg present as MeHg for the six species considered was in the range 83-93%. Positive associations were observed between t-Hg and MeHg content of fish and measures of fish size (length, weight), although the strength of the associations was species dependent. The mean EPA + DHA content of the six fish species varied in the range 2.0-20.5 mg/g. Two approaches were trialled to compare the risks, due to MeHg, and the benefits, due to EPA and DHA, from consumption of the six fish species. Both approaches identify that for these six fish species the benefits of normal patterns of fish consumption on offspring IQ largely outweigh the risks from MeHg.

Spatial variability in Polonium-210 and Lead-210 activity concentration in New Zealand shellfish and dose assessment.

The activity concentrations of Polonium-210 (210Po) and Lead-210 (210Pb) were determined in shellfish (Perna canaliculus and Paphies subtriangulata) sampled bimonthly from March 2018 to February 2019 from 14 sites around New Zealand. Activity concentrations of 210Po ranged from 4.7 ±â€¯1.1 to 324 ±â€¯17 Bq. kg-1 with a mean value of 57 ±â€¯72 Bq. kg-1 (wet weight). The activity concentrations of 210Pb were lower than those for 210Po (0.1 ±â€¯0.4 and 1.9 ±â€¯0.4 Bq. kg-1, with a mean value of 0.7 ±â€¯0.4 Bq. kg-1, wet weight). The calculated 210Po/210Pb activity concentration ratios were higher than unity in all samples indicating that radionuclides are not in equilibrium in shellfish and most of the 210Po was unsupported by its grandparent 210Pb. No significant difference was noted in 210Po activity concentration between different seasons, species or shellfish condition index. Significant spatial variability in 210Po activity concentration was observed with elevated 210Po activity concentration in two sampling sites: Ninety Mile Beach (mean 257 ±â€¯47 Bq. kg-1) and Maunganui Bluff (mean 127 ±â€¯22 Bq. kg-1). Elevated 210Po is hypothesised to be related to an increase of 210Po accumulation through diet. Individuals who consume large quantities of shellfish (10 g per day or more) from areas affected by elevated 210Po activity concentration may be exposed to an annual committed effective dose from 210Po in shellfish in excess of 1 mSv.

Radium in New Zealand agricultural soils: Phosphate fertiliser inputs, soil activity concentrations and fractionation profiles.

Phosphate ores can contain high levels of 238U and its decay products. Of these decay products 226Ra is an important environmental contaminant, while 228Ra from 232 Th day may also be present, albeit at lower activity concentrations. Acid processing of phosphate ore to triple superphosphate elutes a large proportion of the 226Ra from the final product. However, fertiliser production in New Zealand generally avoids acid processing and instead uses single superphosphate and reactive phosphate rock to maintain crop yields, meaning that 226Ra is retained in the final product. As a first step towards characterising the human health impacts from fertiliser-borne radium, research was undertaken to identify loading and long-term accumulation of 226Ra and 228Ra in New Zealand agricultural soils, as well as the fractionation of 226Ra into different soil phases. Activity concentrations for 226Ra of up to 1.6 kBq/kg were determined in phosphate-containing fertilisers used in New Zealand. In contrast, 228Ra did not exceed 75 Bq/kg. Analysis of 40 New Zealand soils, covering a range of agricultural uses, showed activities of between (27-88) Bq/kg 226Ra and (21-102) Bq/kg 228Ra. Unexpectedly, there was also a strong correlation between the two radium isotopes. In 13 of the agricultural soils, all with very high available phosphate levels, the fractionation profile of 226Ra was determined. These data indicated that 226Ra largely remains immobile in the residual phase of the soil. Calcium and available phosphate were significantly correlated with binding of 226Ra into labile and non-labile fractions. Barium is also hypothesised to play a significant role in co-precipitating 226Ra into non-labile soil fractions. While a high percentages of 226Ra immobile in the non-labile fraction would allow for marked accumulation over time it may limit the availability for uptake into crops and thus the ionising radiation dose for consumers.

Impact of Repetitive Mild Traumatic Brain Injury on Behavioral and Hippocampal Deficits in a Mouse Model of Chronic Stress.

Clinical studies examining the interaction between traumatic brain injury (TBI) and stress-related disorders (e.g., post-traumatic stress disorder) are often complicated by methodological constraints, such as heterogeneity in injury type and severity, time post-trauma, and predisposing risk factors. Developing relevant animal models whereby many variables can be efficiently controlled is thus essential to understanding this elusive relationship. Here, we use our repeated unpredictable stress (RUS) paradigm, in combination with our established mouse model of repetitive mild TBI (r-mTBI), to assess the impact of repeated exposures to these paradigms on behavioral and neurobiological measures. C57BL/6J male mice were exposed to RUS and r-mTBI at 3 and 6 months of age followed by batteries of behavioral testing. Mice were euthanized 10 days and 3 months post-exposure, with brain and plasma samples collected for molecular profiling. The RUS paradigm involved exposure to a predator odor (trimethylthiazoline; TMT) while under restraint, daily unstable social housing, five inescapable footshocks on separate days, and chronic social isolation. Animals receiving r-mTBI ( × 5) and stress were exposed to a single closed-head injury 1 h after each footshock. Stress-alone mice showed significant weight loss, recall of traumatic memories, and anxiety-like and passive stress-coping behavior when compared with control mice. However, in stress+r-mTBI animals, the changes in cued fear memory, anxiety, and stress-coping tests were diminished, possibly due to TBI-induced hyperactivity. We also report complex brain molecular and neuropathological findings. Stress and r-mTBI, either individually or comorbidly, were associated with a chronic reduction in dendritic spine GluN2A/GluN2B ratio in the hippocampus. While stress augmented the r-mTBI-dependent astrogliosis in the corpus callosum, it mitigated r-mTBI-induced increases in hippocampal pro-brain-derived neurotrophic factor. We anticipate that our model will be a good platform to untangle the complex comorbid pathophysiology in stress disorders and r-mTBI.

Charge extraction via graded doping of hole transport layers gives highly luminescent and stable metal halide perovskite devices.

One source of instability in perovskite solar cells (PSCs) is interfacial defects, particularly those that exist between the perovskite and the hole transport layer (HTL). We demonstrate that thermally evaporated dopant-free tetracene (120 nm) on top of the perovskite layer, capped with a lithium-doped Spiro-OMeTAD layer (200 nm) and top gold electrode, offers an excellent hole-extracting stack with minimal interfacial defect levels. For a perovskite layer interfaced between these graded HTLs and a mesoporous TiO2 electron-extracting layer, its photoluminescence yield reaches 15% compared to 5% for the perovskite layer interfaced between TiO2 and Spiro-OMeTAD alone. For PSCs with graded HTL structure, we demonstrate efficiency of up to 21.6% and an extended power output of over 550 hours of continuous illumination at AM1.5G, retaining more than 90% of the initial performance and thus validating our approach. Our findings represent a breakthrough in the construction of stable PSCs with minimized nonradiative losses.

Deterministic and Semiprobabilistic Modeling of the Committed Dose from Radionuclides and the Chemical Burden from Uranium in the New Zealand Diet.

To support New Zealand's food safety monitoring, estimates of the current population exposure to ionizing radiation through diet are needed. To calculate the committed dose from radionuclide activities in the food chain, dietary modeling was undertaken for different age and gender groupings of the New Zealand population. Based on a published survey of radionuclide activity concentrations in the New Zealand diet, deterministic and semiprobabilistic models were constructed to derive estimates of the effective dose via the diet. Deterministic estimated annual doses across the different age and gender groupings ranged from a minimum of 48 to 66 µSv/year for teenage girls to a maximum of 126 to 152 µSv/year for adult males. Polonium-210 was the main contributor to ingested dose, with anthropogenic radionuclides contributing very little. For adults, seafood represented the most important source of exposure, with the contribution from this source decreasing for younger age groups. Results of the semiprobabilistic model identified a range of possible ingested doses, with 2.5 to 97.5th percentile ranges of 0.01 to 1.44 µSv/day for adults and 0.02 to 1.84 µSv/day for children. Estimated doses to the New Zealand population show similarities to those of other countries and fall within the expected global range. The current level of exposure to ionizing radiation in the diet does not represent an elevated health risk.