Abstract
To boost the photoelectrochemical water oxidation performance of hematite photoanodes, high temperature annealing has been widely applied to enhance crystallinity, to improve the interface ...between the hematite-substrate interface, and to introduce tin-dopants from the substrate. However, when using additional dopants, the interaction between the unintentional tin and intentional dopant is poorly understood. Here, using germanium, we investigate how tin diffusion affects overall photoelectrochemical performance in germanium:tin co-doped systems. After revealing that germanium is a better dopant than tin, we develop a facile germanium-doping method which suppresses tin diffusion from the fluorine doped tin oxide substrate, significantly improving hematite performance. The NiFeO
x
@Ge-PH photoanode shows a photocurrent density of 4.6 mA cm
−2
at 1.23 V
RHE
with a low turn-on voltage. After combining with a perovskite solar cell, our tandem system achieves 4.8% solar-to-hydrogen conversion efficiency (3.9 mA cm
−2
in NiFeO
x
@Ge-PH/perovskite solar water splitting system). Our work provides important insights on a promising diagnostic tool for future co-doping system design.
In small-area perovskite solar cells, efficiencies of >25% have been achieved using an antisolvent dripping technique; however, it is not applicable for coatings on an industrial scale. Currently, ...large-area devices based on scalable perovskite coatings still show a very large gap with small-area devices. This means that a uniform perovskite coating and defect control on large-area devices are not as secure as they are on small devices. Here, we report the deposition of dense and uniform perovskite films using an air-knife-assisted bar-coating employing a perovskite (FAPbI3)0.95(MAPbBr3)0.05 precursor solution dissolved in 2-methoxyethanol. A pinhole-free and homogeneous surface morphology was achieved by adding n-cyclohexyl-2-pyrrolidone to ensure a balance between rapid nucleation and slowed crystal growth in the precursor solution. By applying surface passivation with acetylcholine bromide and laser etching to thin layers, mini-modules with an aperture area of 31 cm2 were fabricated, attaining an efficiency of >20% (17.53% in the efficiency certified by a quasi-steady-state protocol).
Display omitted
•Large-area perovskite devices are fabricated by the air-knife-assisted bar-coating method•2Me-CHP mixture ensures the balance between rapid nucleation and slowed crystal growth•ACBr effectively passivates the perovskite surface, resulting in Voc enhancement•Laser-patterned perovskite mini-modules exhibit PCE >20%
Although perovskite solar cells are promising as a means of next-generation energy production due to their high power-conversion efficiency (PCE), the PCE of large-area modules still lags far behind that of small-area cells. In this study, high-efficiency and large-area perovskite mini-modules were successfully fabricated using 2-methoxyethanol as a solvent and n-cyclohexyl-2-pyrrolidone as an additive. A balance between fast nucleation and slowed crystal growth was valid for the formation of uniform and dense perovskite films. Furthermore, the efficiency of the devices was significantly improved by reducing the surface defects through surface treatment with acetylcholine bromide. With the addition of the laser scribing process, perovskite mini-modules with an aperture area of 31 cm2 and a PCE of over 20% were fabricated. We believe that the present process will be applicable to the fabrication of larger-area perovskite modules.
Large-area perovskite mini-modules are fabricated under ambient conditions by bar-coating with an air knife using 2-methoxyethanol (2Me), a highly volatile solvent. 2Me induces rapid nucleation, and the addition of small amounts of n-cyclohexyl-2-pyrrolidone contributes to the formation of a uniform thin film by balancing fast nucleation with slow crystal growth. Moreover, acetylcholine bromide bar-coating on the perovskite film helps to heal surface defects. As a result, laser-patterned mini-modules exhibit efficiencies of over 20%.
White LEDs are fabricated through a combination of blue LEDs with Sr3SiO5:Ce3+,Li+ phosphors and organically capped CdSe quantum dots (QDs), which exhibit a 2D superlattice. The combination of blue ...emission from the LEDs, greenish‐yellow emission from the phosphors, and red emission from the QDs generates white light. As‐synthesized white LEDs show excellent color rendering properties and stable color coordinates against increasing forward bias currents (see figure).
Poly(p-phenylene)-based random copolymers with locally and densely sulfonated multi-phenyl pendants, which are promising candidates for hydrocarbon-based electrolyte membrane materials for fuel ...cells, were synthesized using Ni(0)-catalyzed cross-coupling polymerization. The synthesized ionomers, SPPFPB-o, showed outstanding dimensional changes and proton conductivity. The SPPFPB-5.5 membrane in particular had the highest ion exchange capacity (IEC) (2.58meq/g) among the SPPFPB-o series. It exhibited smaller dimensional changes toward the in-plane direction (△l) than that of the Nafion® 212 membrane, in spite of a higher water uptake (WU) value, which seemed to be derived from the rigid backbone structure. Moreover, the SPPFPB-5.5 membrane showed excellent fuel cell performance and long-term stability comparable or superior to those of Nafion® 212 under fully and partially hydrated conditions.
Display omitted
•Poly(p-phenylene)-based ionomers with sulfonated pendants were synthesized.•They showed outstanding dimensional stability.•They showed excellent PEMFC performance as well as durability.
Burnout is a form of negative emotional and physical response to job stress. This study aimed to investigate the prevalence of burnout among healthcare workers responding to the coronavirus disease ...2019 (COVID-19) outbreak in Korea and to explore correlates of burnout among healthcare workers. A nationwide questionnaire-based survey was conducted from December 1, 2020, to January 29, 2021 on 1425 healthcare workers who worked in one of the 16 healthcare facilities designated for COVID-19 care, in public health centers, or as paramedics in Korea. Burnout was assessed using 16 Korean-adapted items based on the Oldenburg Burnout Inventory (OLBI). Data were collected using a structured questionnaire and analyzed using the R version 4.1.1 software program. OLBI results indicate clinically exhaustion in 84.5% (1204/1425) and clinically disengagement in 91.1% (1298/1425), and 77.3% (1102/1425) met the score criteria for both the exhaustion and disengagement subscales for burnout. Burnout rate was significantly increased in the group with chronic fatigue symptoms (Fatigue Severity Scale ≥ 3.22) after the outbreak of COVID-19 (OR, 3.94; 95% CI 2.80-5.56), in the female group (OR, 2.05; 95% CI 1.46-2.86), in the group with physical symptoms (Patient Health Questionnaire-15 ≥ 10) after the outbreak of COVID-19 (OR, 2.03; 95% CI 1.14-3.60), in the group with a higher Global Assessment of Recent Stress scale (OR, 1.71; 95% CI 1.46-2.01), in the group with post-traumatic stress symptoms (Primary Care Post-Traumatic Stress Disorder-5 ≥ 2) (OR, 1.47; 95% CI 1.08-2.01), and in the younger age group(OR, 1.45; 95% CI 1.22-1.72). The chronic fatigue symptoms were correlated with cumulative days of care (OR, 1.18; 95% CI 1.02-1.37). The physical symptoms were correlated with average contact hours with COVID-19 patients per day (OR, 1.34; 95% CI 1.17-1.54), and cumulative days of care (OR, 1.21; 95% CI 1.06-1.38). Most Korean healthcare workers suffered from burnout related to excessive workload during the COVID-19 pandemic. During a widespread health crisis like COVID-19, it is necessary to regularly check the burnout status in healthcare workers and reduce their excessive workload by supplementing the workforce and providing appropriate working hours sufficient rest hours.
Inorganic electron transport layers (ETLs), such as titanium dioxide (TiO2) and tin dioxide (SnO2), are important in n–i–p structured perovskite solar cells (PSCs). In particular, the ETLs for ...flexible PSCs (f-PSCs) using a polymer substrate require strong adhesion with a transparent conducting oxide (TCO) and formation of a uniform thin film at a temperature below 150 °C. Hence, SnO2 colloidal nanoparticles are primarily used to meet these demands. Nevertheless, there exist further opportunities for improvement in terms of efficiency, uniform coating, and adhesion on TCO. In this study, we prepared a SnO2–TiO2 hybrid electrode by adding a certain amount of TiO2 nanosol, which functions as an inorganic binder, to a SnO2 colloidal solution. In comparison with the SnO2 colloid alone, f-PSC fabricated with a SnO2–TiO2 hybrid electrode demonstrated not only better mechanical reliability against bending due to strong adhesion to the substrate but also greatly improved efficiency because of improved energy alignment. Eventually, the SnO2–TiO2 hybrid electrode resulted in an efficiency of 21.02% and even an efficiency of over 16% in a mini-module (7 × 7 cm2) due to the uniform coating over a large area. This study provides a new strategy for the ETL of high-efficiency f-PSCs.
Throughout the coronavirus disease 2019 (COVID-19) pandemic, not only medical personnel but also paramedics or emergency medical technicians (EMT) have faced multiple physical and psychological ...challenges while performing their duties. The current study aimed to evaluate the psychological effects of managing patients with COVID-19 on the paramedics and EMT.
A survey targeting paramedics and EMT in Korea was conducted in December 2020. An official letter requesting participation and with the link to an online-based survey was sent to the Public Emergency Medical Services. Only one response was accepted from each participant.
A total of 326 paramedics and EMT responded to the survey. Among them, 66.3% (216/326) had experience in managing patients with COVID-19. No differences in the distribution of sex, age, working area, duration of working experience, and underlying comorbidities were observed between those who did (COVID-19 group) and did not (non-COVID-19 group) experience managing patients with COVID-19. The percentage of participants who showed severe posttraumatic stress disorder (PTSD) symptoms was significantly higher in the COVID group than in the non-COVID group (11.1%
3.6%,
= 0.029). The participants in the COVID group had a significantly higher mean Global Assessment of Recent Stress Scale score than those in the non-COVID group (18.7 ± 11.1
16.1 ± 9.9,
= 0.042). The proportion of paramedics and EMT willing to leave their job if given a chance was higher in the COVID group than the non-COVID group (24.1%
9.1%,
= 0.001). Additionally, paramedics and EMT in the COVID group tended to show concern regarding exposure to COVID-19 infection.
The experience of managing patients with COVID-19 resulted in psychological distress among paramedics and EMT in Korea.
A healthcare system's collapse due to a pandemic, such as the coronavirus disease 2019 (COVID-19), can expose healthcare workers (HCWs) to various mental health problems. This study aimed to ...investigate the impact of the COVID-19 pandemic on the depression and anxiety of HCWs.
A nationwide questionnaire-based survey was conducted on HCWs who worked in healthcare facilities and public health centers in Korea in December 2020. Patient Health Questionnaire-9 (PHQ-9) and Generalized Anxiety Disorder-7 (GAD-7) were used to measure depression and anxiety. To investigate factors associated with depression and anxiety, stepwise multiple logistic regression analysis was performed.
A total of 1,425 participating HCWs were included. The mean depression score (PHQ-9) of HCWs before and after COVID-19 increased from 2.37 to 5.39, and the mean anxiety score (GAD-7) increased from 1.41 to 3.41. The proportion of HCWs with moderate to severe depression (PHQ-9 ≥ 10) increased from 3.8% before COVID-19 to 19.5% after COVID-19, whereas that of HCWs with moderate to severe anxiety (GAD-7 ≥ 10) increased from 2.0% to 10.1%. In our study, insomnia, chronic fatigue symptoms and physical symptoms after COVID-19, anxiety score (GAD-7) after COVID-19, living alone, and exhaustion were positively correlated with depression. Furthermore, post-traumatic stress symptoms, stress score (Global Assessment of Recent Stress), depression score (PHQ-9) after COVID-19, and exhaustion were positively correlated with anxiety.
In Korea, during the COVID-19 pandemic, HCWs commonly suffered from mental health problems, including depression and anxiety. Regularly checking the physical and mental health problems of HCWs during the COVID-19 pandemic is crucial, and social support and strategy are needed to reduce the heavy workload and psychological distress of HCWs.
PDF
