Graphene-perovskite fibre photodetectors

The integration of optoelectronic devices, such as transistors and photodetectors (PDs), into wearables and textiles is of great interest for applications such as healthcare and physiological monitoring. These require flexible/wearable systems adaptable to body motions, thus materials conformable to non-planar surfaces, and able to maintain performance under mechanical distortions. Here, we prepare fibre PDs combining rolled graphene layers and photoactive perovskites. Conductive fibres ($\sim$500$\Omega$/cm) are made by rolling single layer graphene (SLG) around silica fibres, followed by deposition of a dielectric layer (Al$_{2}$O$_{3}$ and parylene C), another rolled SLG as channel, and perovskite as photoactive component. The resulting gate-tunable PDs have response time$\sim$5ms, with an external responsivity$\sim$22kA/W at 488nm for 1V bias. The external responsivity is two orders of magnitude higher and the response time one order of magnitude faster than state-of-the-art wearable fibre based PDs. Under bending at 4mm radius, up to$\sim$80\% photocurrent is maintained. Washability tests show$\sim$72\% of initial photocurrent after 30 cycles, promising for wearable applications

Postnatal quality of life in women after normal vaginal delivery and caesarean section

<p>Abstract</p> <p>Background</p> <p>Caesarean section might increase the incidence of surgical interventions and problems resulting from hospitalization and thus affecting quality of life in women after delivery. This study aimed to compare quality of life in women after normal delivery and caesarean section.</p> <p>Methods</p> <p>This was a prospective study. A sample of women with normal delivery and caesarean section from 5 health care centers in Isfahan, Iran were entered into the study. Quality of life was measured using the SF-36 at two points in time (time 1: 6 to 8 weeks after delivery; time 2: 12 to 14 weeks after delivery). Data were analyzed to compare quality of life in the two study groups.</p> <p>Results</p> <p>In all 100 women were interviewed (50 with normal delivery and 50 with caesarean section). Postnatal quality of life in both groups was improved from time1 to time 2. However, comparing the mean scores between the normal and caesarean delivery groups the results showed that in general the normal vaginal delivery group had a better quality of life for almost all subscales in both assessment times. The differences were significant for vitality (mean score 62.9 vs. 54.4 P = 0.03) and mental health (mean score 75.1 vs. 66.7, P = 0.03) at first assessment and for physical functioning (mean score 88.4 vs. 81.5, P = 0.03) at second evaluation. However, comparing the findings within each group the analysis showed that the normal vaginal delivery group improved more on physical health related quality of life while the caesarean section group improved more on mental health related quality of life.</p> <p>Conclusion</p> <p>Although the study did not show a clear cut benefit in favor of either methods of delivery that are normal vaginal delivery or caesarean section, the findings suggest that normal vaginal delivery might lead to a better quality of life especially resulting in a superior physical health. Indeed in the absence of medical indications normal vaginal delivery might be better to be considered as the first priority in term pregnancy.</p

Genetic Basis of Myocarditis: Myth or Reality?

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Health promoting lifestyle and its determinants among university students in Sabzevar, Iran

Background: Healthy lifestyle is a major strategy to promote current and subsequent health status. The aim of this study was to assess the status of health-promoting the lifestyle and its determinants among students. Methods: A stratified random sample of 500 students in a university in the city of Sabzevar, Iran participated in this cross-sectional study. Health-promoting lifestyle was measured using Walker�s health-promoting lifestyle profile II. Results: There was a significant correlation between all domains of health-promoting the lifestyle. The highest score among the domains was for an interpersonal relationship (70.8), and the lowest score was for nutrition (53.6), and physical activity (53.4). Significant differences were found in physical activity by gender (P � 0.05). There were significant differences in health responsibility, spiritual growth and body mass index by marital status (P < 0.01). Conclusions: Since one out of five students in this study were overweight/obese, health program planning to promote lifestyle, especially physical activity and nutrition among students is recommended. Our findings may be helpful for faculty administrators, curriculum planners, and health educators in designing guidelines to structuralize a healthier campus and to develop health promotion programs supporting healthy choices among students. © 2016 International Journal of Preventive Medicine

From Bulk to Surface Passivation: Double Role of Chlorine-Doping for Boosting Efficiency of FAPbI<inf>3</inf>-rich Perovskite Solar Cells

Funder: Green flexible hybrid perovskite solar module for the market: from smart lead manipulation to recycling; Grant(s): FLHYPER, 20201067Defect‐mediated recombination losses limit the open‐circuit voltage (VOC) of perovskite solar cells (PSCs), negatively affecting the device's performance. Bulk and dimensional engineering have both been reported as promising strategies to passivate shallow defects, thus improving the photovoltaic conversion efficiency (PCE). Here, a combined bulk and surface treatment employing chlorine‐based compounds is employed. Methylammonium chloride (MACl) is used as a bulk additive, while 4‐methylphenethylammonium chloride (MePEACl) is deposited onto the perovskite surface to produce a low‐dimensional perovskite (LDP) and reduce nonradiative recombination. Through structural and morphological investigations, it can be confirmed that bulk and surface doping have a beneficial effect on the film morphology and its overall quality, while electroluminescence (EL) and photoluminescence (PL) analyses demonstrate an increased and more homogeneous emission. Applying this double passivation strategy in PSC fabrication, a boost is observed in both the short‐circuit current density and the VOC of the devices, achieving a champion 21.4% PCE while improving device stability

From Bulk to Surface Passivation: Double Role of Chlorine-Doping for Boosting Efficiency of FAPbI(3)-rich Perovskite Solar Cells

Defect-mediated recombination losses limit the open-circuit voltage (V-OC) of perovskite solar cells (PSCs), negatively affecting the device's performance. Bulk and dimensional engineering have both been reported as promising strategies to passivate shallow defects, thus improving the photovoltaic conversion efficiency (PCE). Here, a combined bulk and surface treatment employing chlorine-based compounds is employed. Methylammonium chloride (MACl) is used as a bulk additive, while 4-methylphenethylammonium chloride (MePEACl) is deposited onto the perovskite surface to produce a low-dimensional perovskite (LDP) and reduce nonradiative recombination. Through structural and morphological investigations, it can be confirmed that bulk and surface doping have a beneficial effect on the film morphology and its overall quality, while electroluminescence (EL) and photoluminescence (PL) analyses demonstrate an increased and more homogeneous emission. Applying this double passivation strategy in PSC fabrication, a boost is observed in both the short-circuit current density and the V-OC of the devices, achieving a champion 21.4% PCE while improving device stability

Manipulating Color Emission in 2D Hybrid Perovskites by Fine Tuning Halide Segregation: A Transparent Green Emitter

Halide perovskite materials offer an ideal playground for easily tuning their color and, accordingly, the spectral range of their emitted light. In contrast to common procedures, this work demonstrates that halide substitution in Ruddlesden–Popper perovskites not only progressively modulates the bandgap, but it can also be a powerful tool to control the nanoscale phase segregation—by adjusting the halide ratio and therefore the spatial distribution of recombination centers. As a result, thin films of chloride-rich perovskite are engineered—which appear transparent to the human eye—with controlled tunable emission in the green. This is due to a rational halide substitution with iodide or bromide leading to a spatial distribution of phases where the minor component is responsible for the tunable emission, as identified by combined hyperspectral photoluminescence imaging and elemental mapping. This work paves the way for the next generation of highly tunable transparent emissive materials, which can be used as light-emitting pixels in advanced and low-cost optoelectronics

Graphene‐Perovskite Fibre Photodetectors

Publication status: PublishedFunder: Royal Society; doi: http://dx.doi.org/10.13039/501100000288The integration of optoelectronic devices, such as transistors and photodetectors (PDs), into wearables and textiles is of great interest for applications such as healthcare and physiological monitoring. These require flexible/wearable systems adaptable to body motions, thus materials conformable to non‐planar surfaces, and able to maintain performance under mechanical distortions. Here, fibre PDs are prepared by combining rolled graphene layers and photoactive perovskites. Conductive fibres (~500 Ωcm‐1) are made by rolling single‐layer graphene (SLG) around silica fibres, followed by deposition of a dielectric layer (Al2O3 and parylene C), another rolled SLG as a channel, and perovskite as photoactive component. The resulting gate‐tunable PD has a response time~9ms, with an external responsivity~22kAW‐1 at 488nm for a 1V bias. The external responsivity is two orders of magnitude higher, and the response time one order of magnitude faster, than state‐of‐the‐art wearable fibre‐based PDs. Under bending at 4mm radius, up to~80% photocurrent is maintained. Washability tests show~72% of initial photocurrent after 30 cycles, promising for wearable applications

Beyond 17% stable perovskite solar module via polaron arrangement of tuned polymeric hole transport layer

Operational stability of perovskite solar cells (PSCs) is rapidly becoming one of the pressing bottlenecks for their upscaling and integration of such promising photovoltaic technology. Instability of the hole transport layer (HTL) has been considered as one of the potential origins of short life-time of the PSCs. In this work, by varying the molecular weight (MW) of doped poly(triarylamine) (PTAA) HTL, we improved by one order of magnitude the charge mobility inside the HTL and the charge transfer at the perovskite/HTL interface. We demonstrate that this occurs via the enhancement of polaron delocalization on the polymeric chains through the combined effect of doping strategy and MW tuning. By using high MW PTAA doped combining three different dopant, we demonstrate stable PSCs with typical power conversion efficiencies above 20%, retain more than 90% of the initial efficiency after 1080 hours thermal stress at 85 ⁰C and 87% of initial efficiency after 160 hours exposure against 1 sun light soaking. By using this doping-MW strategy, we realized perovskite solar modules with an efficiency of 17% on an active area of 43 cm2, keeping above 90% of the initial efficiency after 800 hours thermal stress at 85 ⁰C. These results, obtained in ambient conditions, pave the way toward the industrialization of PSC-based photovoltaic technology.Horizon 2020, Ministry of Education and Science of the Russian Federation, Alexander von Humboldt Foundation, German Federal Ministry of Education and Research, Winton Studentship, Lloyd's Register Foundation, Jardine Foundation, Cambridge Trust, EPSR