Organic p‐type semiconductors with tunable structures offer great opportunities for hybrid perovskite solar cells (PVSCs). We report herein two dithieno3,2‐b:2′,3′‐dpyrrole (DTP) cored molecular ...semiconductors prepared through π‐conjugation extension and an N‐alkylation strategy. The as‐prepared conjugated molecules exhibit a highest occupied molecular orbital (HOMO) level of −4.82 eV and a hole mobility up to 2.16×10−4 cm2 V−1 s−1. Together with excellent film‐forming and over 99 % photoluminescence quenching efficiency on perovskite, the DTP based semiconductors work efficiently as hole‐transporting materials (HTMs) for n‐i‐p structured PVSCs. Their dopant‐free MA0.7FA0.3PbI2.85Br0.15 devices exhibit a power conversion efficiency over 20 %, representing one of the highest values for un‐doped molecular HTMs based PVSCs. This work demonstrates the great potential of using a DTP core in designing efficient semiconductors for dopant‐free PVSCs.
Cores and effect: Dithieno3,2‐b:2′,3′‐dpyrrole cored p‐type semiconductors are developed as dopant‐free hole‐transport materials for perovskite solar cells with an efficiency surpassing 20 %. The modification via π‐conjugation extension and N‐alkylation fine‐tunes the HOMO energy levels, hole mobility, solubility, and film‐forming characteristics.
The unsatisfactory performance of low‐bandgap mixed tin (Sn)–lead (Pb) halide perovskite subcells has been one of the major obstacles hindering the progress of the power conversion efficiencies ...(PCEs) of all‐perovskite tandem solar cells. By analyzing dark‐current density and distribution, it is identified that charge recombination at grain boundaries is a key factor limiting the performance of low‐bandgap mixed Sn–Pb halide perovskite subcells. It is further found that bromine (Br) incorporation can effectively passivate grain boundaries and lower the dark current density by two–three orders of magnitude. By optimizing the Br concentration, low‐bandgap (1.272 eV) mixed Sn–Pb halide perovskite solar cells are fabricated with open‐circuit voltage deficits as low as 0.384 V and fill factors as high as 75%. The best‐performing device demonstrates a PCE of >19%. The results suggest an important direction for improving the performance of low‐bandgap mixed Sn–Pb halide perovskite solar cells.
Charge recombination at grain boundaries is a key factor limiting the performance of low‐bandgap mixed tin–lead halide perovskite solar cells. It is found that bromine incorporation can passivate grain boundaries and lower the dark current density by two to three orders of magnitude. The champion cell shows an open‐circuit voltage deficit of 0.384 V and power conversion efficiency exceeding 19%.
Formamidinium lead triiodide (FAPbI3) is considered as an alternative to methylammonium lead triiodide (MAPbI3) because of its lower band gap and better thermal stability. However, owing to the large ...size of FA cations, it is difficult to synthesize high‐quality FAPbI3 thin films without the formation of an undesirable yellow phase. Smaller sized cations, such as MA and Cs, have been successfully used to suppress the formation of the yellow phase. Whereas FA and MA lead triiodide perovskite solar cells (PVSCs) have achieved power conversion efficiencies (PCEs) higher than 20 %, the PCEs of formamidinium and cesium lead triiodide (FA1−xCsxPbI3) PVSCs have been only approximately 16.5 %. Herein, we report our examination of the main factors limiting the PCEs of (FA1−xCsxPbI3) PVSCs. We find that one of the main limiting factors could be the small grain sizes (≈120 nm), which leads to relatively short carrier lifetimes. We further find that adding a small amount of lead thiocyanate Pb(SCN)2 to the precursors can enlarge the grain size of (FA1−xCsxPbI3) perovskite thin films and significantly increase carrier lifetimes. As a result, we are able to fabricate (FA1−xCsxPbI3) PVSCs with significantly improved open‐circuit voltages and fill factors and, therefore, enhanced PCEs. With an optimal 0.5 mol % Pb(SCN)2 additive, the average PCE is increased from 16.18±0.50 (13.45±0.78) % to 18.16±0.54 (16.86±0.63) % for planar FA0.8Cs0.2PbI3 PVSCs if measured under reverse (forward) voltage scans. The champion cell registers a PCE of 19.57 (18.12) % if measured under a reverse (forward) voltage scan, which is comparable to that of the best‐performing MA‐containing planar FA‐based lead halide PVSCs.
The effects of additives: The power conversion efficiency (PCE) of mixed formamidinium (FA) and cesium lead triiodide perovskite solar cells is improved by introducing lead thiocyanate additives. The best PCE is improved from 17.61 to 19.57 % and the effect of additives is thoroughly studied. Voc=open‐circuit voltage, Jsc=short‐circuit current density, FF=fill factor.
In eukaryotic cells, there are two well characterized pathways that regulate translation initiation in response to stress, and each have been shown to be targeted by various viruses. We recently ...showed in a yeast-based model that the bacterial virulence factor YopJ disrupts one of these pathways, which is centered on the α-subunit of the translation factor eIF2. Here, we show in mammalian cells that induction of the eIF2 signaling pathway occurs following infection with bacterial pathogens and that, consistent with our yeast-based findings, YopJ reduces eIF2 signaling in response to endoplasmic reticulum stress, heavy metal toxicity, dsRNA, and bacterial infection. We demonstrate that the well documented activities of YopJ, inhibition of NF-κB activation and proinflammatory cytokine expression, are both dependent on an intact eIF2 signaling pathway. Unexpectedly, we found that cells with defective eIF2 signaling were more susceptible to bacterial invasion. This was true for pathogenic Yersinia, a facultative intracellular pathogen, as well as for the intracellular pathogens Listeria monocytogenes and Chlamydia trachomatis. Collectively, our data indicate that the highly conserved eIF2 signaling pathway, which is vitally important for antiviral responses, plays a variety of heretofore unrecognized roles in antibacterial responses.
Background: eIF2 is a critical point of stress-induced regulation of translation in eukaryotic cells.
Results: eIF2 signaling is activated by bacterial pathogens and regulates two key infection-associated processes.
Conclusion: Regulation of translation in eukaryotic cells is involved in innate immune responses.
Significance: These findings enlarge the possible targets for therapeutic interventions against bacterial pathogens.
Globally violence is a matter of public health concern with severe physical and mental health implications and social consequences. Evidence suggest that adolescents have an elevated risk of exposure ...to physical and sexual violence. However, there is a lack of nationally representative research on violence and its associated factors in Nepal to inform interventions. This paper attempts to find the factors associated with various forms of physical and sexual violence among school-going adolescents in Nepal.
We analysed the cross-sectional data from the Global School-based Student Health Survey (GSHS) 2015. The GSHS survey applied a two-stage cluster sampling process to select a representative sample of 7 to 11 grade students from 74 schools across the country. We applied logistic regression analysis to identify the factors associated with physical and sexual violence.
Out of the total 6,529 participants, 45.24% of them faced a physical attack, 39.25% were involved in a physical fight, and 11.65% were victims of sexual violence in the survey administered between 7 August 2015 to 14 March 2016. In a multiple regression analysis, the age of participants, parental supervision, feeling unsafe at school, and the number of close friends were found to be associated with a physical attack. Participants who were bullied, had multiple sex partners, and had received corporal punishment in school had a higher engagement in a physical fight. Likewise, school grade, having parents who understand the problems, having multiple sex partners, and corporal punishment at school were associated with instances of sexual violence.
The study identified multiple factors associated with experiences of physical attacks, involvement in a physical fight, and sexual violence among school-going adolescents. This study results can have important implications for school administration, parents, and policymakers alike to plan appropriate anti-violence strategies and interventions. Since various forms of violence share some common risk factors, a comprehensive strategy could be worth considering to prevent such acts of violence.
Between 1990 and 2017, Nepal experienced a shift in the burden of disease from communicable, maternal, neonatal and nutritional (CMNN) diseases to non-communicable diseases (NCDs). With an increasing ...ageing population and life-style changes including tobacco use, harmful alcohol consumption, unhealthy diets, and insufficient physical activity, the proportion of total deaths from NCDs will continue to increase. An analysis of current diseases pattern and projections of the trends informs planning of health interventions. This analysis aims to project the mortality and risk factor of disease until 2040, based on past trends.
This study uses secondary data from the Global Burden of Disease (GBD) Study which analyses historic data from 1990 to 2016 to predict key variables such as, the mortality rates, life expectancy and Years of Life Lost for different causes of death from 2017 to 2040. 'GBD Foresight Visualization', a visualisation tool publicly available in the webpage of Institute for Health Metrics and Evaluation was the source of data for this analysis. GBD forecasting uses three-component modelling process: the first component captures variations due to risk factors and interventions, the second takes into consideration the variation due to measures of development quantified as social development index and the third uses an autoregressive integrated moving average model to capture the unexplained component correlated over time. We extracted Nepal specific data from it and reported number of deaths, mortality rates (per 100,000 population) as well as causes of death for the period 1990 to 2040.
In 1990, CMNN diseases were responsible for approximately two-thirds (63.6%) of total deaths in Nepal. The proportion of the deaths from the CMNN diseases has reduced to 26.8% in 2015 and is estimated to be about a fifth of the 1990 figure (12.47%) in 2040. Conversely, deaths from NCDs reflect an upward trend. NCDs claimed a third of total deaths (29.91%) in the country in 1990, while in 2015, were responsible for about two-thirds of the total deaths (63.31%). In 2040, it is predicted that NCDs will contribute to over two-thirds (78.64%) of total deaths in the country. Less than a tenth (6.49%) of the total deaths in Nepal in 1990 were associated with injuries which increased to 13.04% in 2015 but is projected to decrease to 8.89% in 2040. In 1990, metabolic risk factors including high systolic blood pressure, high total cholesterol, high fasting plasma glucose, high body mass index and impaired kidney functions collectively contributed to a tenth of the total deaths (10.38%) in Nepal, whereas, in 2040 more than a third (37.31%) of the total deaths in the country could be attributed to it.
A reverse of the situation in 1990, NCDs are predicted to be the leading cause of deaths and metabolic risk factors are predicted to contribute to the highest proportion of deaths in 2040. NCDs could demand a major share of resources within the health sector requiring extensive multi-sectoral prevention measures, re-allocation of resources and re-organisation of the health system to cater for long-term care.
A carbazole-based hole-transporting material named 4,4′,4′′,4′′′-(9-octylcarbazole-1,3,6,8-tetrayl) tetrakis(N,N-bis(4-methoxyphenyl)aniline) (CZ-TA) has been developed through a one-step facile ...synthesis approach. The solution-processed planar perovskite solar cells (PVSCs) with 50nm thick CZ-TA hole selective layer (HSL) contributes a power conversion efficiency of 18.32%, comparable to the most commonly used 200nm spiro-OMeTAD (18.28%) HSLs. The improved hole extraction, transport and reduced recombination are found to endow CZ-TA-based devices with impressive fill factors over 81.0%. Importantly, the unit cost of HSL in PVSCs using CZ-TA can be as low as only 1/80 of that of spiro-OMeTAD, indicating that CZ-TA could be a promising candidate as HSLs for commercialization of the low-cost PVSC technology.
One-step facilely synthesized carbazole-cored hole transport material has afforded the solution-processed perovskite solar cells with a maximum power conversion efficiency of 18.32%, comparable to that of the mostly used spiro-OMeTAD. The unit cost of hole transport layer can be cut down to 1/80 of that of spiro-OMeTAD by using this new material. Display omitted
•Cabazole-based hole-transporting material CZ-TA was developed via one-step synthesis.•Perovskite solar cells (PVSCs) with 50nm CZ-TA film achieved a maximum PCE of 18.32%, comparable to that with 200nm spiro-OMeTAD.•CZ-TA improved the hole extraction and transport to afford impressive fill factors over 81%.•The unit cost of CZ-TA hole-transporting layer was only 1/80 of that of spiro-OMeTAD, paving its way for commercialization of low-cost PVSC technology.
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