Lead immobilization for environmentally sustainable perovskite solar cells.

Lead halide perovskites are promising semiconducting materials for solar energy harvesting. However, the presence of heavy-metal lead ions is problematic when considering potential harmful leakage into the environment from broken cells and also from a public acceptance point of view. Moreover, strict legislation on the use of lead around the world has driven innovation in the development of strategies for recycling end-of-life products by means of environmentally friendly and cost-effective routes. Lead immobilization is a strategy to transform water-soluble lead ions into insoluble, nonbioavailable and nontransportable forms over large pH and temperature ranges and to suppress lead leakage if the devices are damaged. An ideal methodology should ensure sufficient lead-chelating capability without substantially influencing the device performance, production cost and recycling. Here we analyse chemical approaches to immobilize Pb2+ from perovskite solar cells, such as grain isolation, lead complexation, structure integration and adsorption of leaked lead, based on their feasibility to suppress lead leakage to a minimal level. We highlight the need for a standard lead-leakage test and related mathematical model to be established for the reliable evaluation of the potential environmental risk of perovskite optoelectronics.

Stability-limiting heterointerfaces of perovskite photovoltaics.

Optoelectronic devices consist of heterointerfaces formed between dissimilar semiconducting materials. The relative energy-level alignment between contacting semiconductors determinately affects the heterointerface charge injection and extraction dynamics. For perovskite solar cells (PSCs), the heterointerface between the top perovskite surface and a charge-transporting material is often treated for defect passivation1-4 to improve the PSC stability and performance. However, such surface treatments can also affect the heterointerface energetics1. Here we show that surface treatments may induce a negative work function shift (that is, more n-type), which activates halide migration to aggravate PSC instability. Therefore, despite the beneficial effects of surface passivation, this detrimental side effect limits the maximum stability improvement attainable for PSCs treated in this way. This trade-off between the beneficial and detrimental effects should guide further work on improving PSC stability via surface treatments.

Artificial Synapse Based on a δ-FAPbI3/Atomic-Layer-Deposited SnO2 Bilayer Memristor.

Halide perovskite-based resistive switching memory (memristor) has potential in an artificial synapse. However, an abrupt switch behavior observed for a formamidinium lead triiodide (FAPbI3)-based memristor is undesirable for an artificial synapse. Here, we report on the δ-FAPbI3/atomic-layer-deposited (ALD)-SnO2 bilayer memristor for gradual analogue resistive switching. In comparison to a single-layer δ-FAPbI3 memristor, the heterojunction δ-FAPbI3/ALD-SnO2 bilayer effectively reduces the current level in the high-resistance state. The analog resistive switching characteristics of δ-FAPbI3/ALD-SnO2 demonstrate exceptional linearity and potentiation/depression performance, resembling an artificial synapse for neuromorphic computing. The nonlinearity of long-term potentiation and long-term depression is notably decreased from 12.26 to 0.60 and from -8.79 to -3.47, respectively. Moreover, the δ-FAPbI3/ALD-SnO2 bilayer achieves a recognition rate of ≤94.04% based on the modified National Institute of Standards and Technology database (MNIST), establishing its potential in an efficient artificial synapse.

Effects of MgF2anti-reflection coating on optical losses in metal halide perovskite solar cells.

The importance of light management for perovskite solar cells (PSCs) has recently been emphasized because their power conversion efficiency approaches their theoretical thermodynamic limits. Among optical strategies, anti-reflection (AR) coating is the most widely used method to reduce reflectance loss and thus increase light-harvesting efficiency. Monolayer MgF2is a well-known AR material because of its optimal refractive index, simple fabrication process, and physical and chemical durabilities. Nevertheless, quantitative estimates of the improvement achieved by the MgF2AR layer are lacking. In this study, we conducted theoretical and experimental evaluations to assess the AR effect of MgF2on the performance of formamidinium lead-triiodide PSCs. A sinusoidal tendency to enhance the short-circuit current density (JSC) was observed depending on the thickness, which was attributed to the interference of the incident light. A transfer matrix method-based simulation was conducted to calculate the optical losses, demonstrating the critical impact of reflectance loss on theJSCimprovement. The predictedJSCs values, depending on the perovskite thickness and the incident angle, are also presented. The combined use of experimental and theoretical approaches offers notable advantages, including accurate interpretation of photocurrent generation, detailed optical analysis of the experimental results, and device performance predictions under unexplored conditions.

Suppressing ion migration in metal halide perovskite via interstitial doping with a trace amount of multivalent cations.

Cations with suitable sizes to occupy an interstitial site of perovskite crystals have been widely used to inhibit ion migration and promote the performance and stability of perovskite optoelectronics. However, such interstitial doping inevitably leads to lattice microstrain that impairs the long-range ordering and stability of the crystals, causing a sacrificial trade-off. Here, we unravel the evident influence of the valence states of the interstitial cations on their efficacy to suppress the ion migration. Incorporation of a trivalent neodymium cation (Nd3+) effectively mitigates the ion migration in the perovskite lattice with a reduced dosage (0.08%) compared to a widely used monovalent cation dopant (Na+, 0.45%). The photovoltaic performances and operational stability of the prototypical perovskite solar cells are enhanced with a trace amount of Nd3+ doping while minimizing the sacrificial trade-off.

Helicobacter pylori Empirical and Tailored Eradication Therapy and Factors Influencing Eradication Rate: a 4-Year Single-Center Study.

BACKGROUND: The Helicobacter pylori eradication rate with standard triple therapy (STT) is continuously decreasing due to clarithromycin resistance. This study aimed to investigate the eradication rate of empirical and tailored therapy and explore various factors affecting this eradication rate using clarithromycin resistance test data for the last 4 years at a single institution in Daegu. METHODS: From August 2018 to July 2021, a total of 1,395 patients diagnosed with H. pylori infection based on rapid urea testing and histology at Keimyung University Dongsan Hospital were retrospectively examined. Participants were classified into the empirical and tailored therapy groups according to the results of the clarithromycin resistance test using the polymerase chain reaction. RESULTS: The overall eradication rate of empirical STT was 72.8%, and the eradication rate by year was 71.6% in 2018, 77.4% in 2019, 70.3% in 2020, and 70.6% in 2021; the differences were not statistically significant (p = 0.173). No significant difference was noted in the eradication rate according to gender, age, type of proton pump inhibitors, and use of probiotics. Significant differences were noted in the eradication rate according to the treat-ment period: 69.7% in the 7-day, 67.3% in the 10-day, and 81.4% in the 14-day group (p = 0.001). The eradication rate with STT was 87.4% in the non-resistant group. In the case of clarithromycin resistance, treatment was mainly with bismuth quadruple therapy (BQT), and the eradication rate was 86.1%. The eradication rate was higher with administration of BQT for 10 days or 14 days than for administration of BQT for 7 days, but with no statistical significance (p = 0.364). CONCLUSIONS: Extending the treatment period of STT helped in improving the eradication rate, and tailored therapy through clarithromycin resistance testing showed superior results when compared to empirical therapy.

The Monitoring and Management of an Operating Environment to Enhance the Safety of a Container-Type Energy Storage System.

The implementation of an energy storage system (ESS) as a container-type package is common due to its ease of installation, management, and safety. The control of the operating environment of an ESS mainly considers the temperature rise due to the heat generated through the battery operation. However, the relative humidity of the container often increases by over 75% in many cases because of the operation of the air conditioner which pursues temperature-first control. Humidity is a major factor which can cause safety issues such as fires owing to insulation breakdown caused by condensation. However, the importance of humidity control in ESS is underestimated compared to temperature control. In this study, temperature and humidity monitoring and management issues were addressed for a container-type ESS by building sensor-based monitoring and control systems. Furthermore, a rule-based air conditioner control algorithm was proposed for temperature and humidity management. A case study was conducted to compare the conventional and proposed control algorithms and verify the feasibility of the proposed algorithm. The results showed that the proposed algorithm reduced the average humidity by 11.4% compared to the value achieved with the existing temperature control method while also maintaining the temperature.

High-Efficiency Perovskite Solar Cells.

With rapid progress in a power conversion efficiency (PCE) to reach 25%, metal halide perovskite-based solar cells became a game-changer in a photovoltaic performance race. Triggered by the development of the solid-state perovskite solar cell in 2012, intense follow-up research works on structure design, materials chemistry, process engineering, and device physics have contributed to the revolutionary evolution of the solid-state perovskite solar cell to be a strong candidate for a next-generation solar energy harvester. The high efficiency in combination with the low cost of materials and processes are the selling points of this cell over commercial silicon or other organic and inorganic solar cells. The characteristic features of perovskite materials may enable further advancement of the PCE beyond those afforded by the silicon solar cells, toward the Shockley-Queisser limit. This review summarizes the fundamentals behind the optoelectronic properties of perovskite materials, as well as the important approaches to fabricating high-efficiency perovskite solar cells. Furthermore, possible next-generation strategies for enhancing the PCE over the Shockley-Queisser limit are discussed.

New developments on the Encyclopedia of DNA Elements (ENCODE) data portal.

The Encyclopedia of DNA Elements (ENCODE) is an ongoing collaborative research project aimed at identifying all the functional elements in the human and mouse genomes. Data generated by the ENCODE consortium are freely accessible at the ENCODE portal (https://www.encodeproject.org/), which is developed and maintained by the ENCODE Data Coordinating Center (DCC). Since the initial portal release in 2013, the ENCODE DCC has updated the portal to make ENCODE data more findable, accessible, interoperable and reusable. Here, we report on recent updates, including new ENCODE data and assays, ENCODE uniform data processing pipelines, new visualization tools, a dataset cart feature, unrestricted public access to ENCODE data on the cloud (Amazon Web Services open data registry, https://registry.opendata.aws/encode-project/) and more comprehensive tutorials and documentation.

Surface Reconstruction of Halide Perovskites During Post-treatment.

Postfabrication surface treatment strategies have been instrumental to the stability and performance improvements of halide perovskite photovoltaics in recent years. However, a consensus understanding of the complex reconstruction processes occurring at the surface is still lacking. Here, we combined complementary surface-sensitive and depth-resolved techniques to investigate the mechanistic reconstruction of the perovskite surface at the microscale level. We observed a reconstruction toward a more PbI2-rich top surface induced by the commonly used solvent isopropyl alcohol (IPA). We discuss several implications of this reconstruction on the surface thermodynamics and energetics. Particularly, our observations suggest that IPA assists in the adsorption process of organic ammonium salts to the surface to enhance their defect passivation effects.

Risk factors for rebleeding in Crohn's disease patients with acute severe lower gastrointestinal bleeding: With special reference to the role of anti-tumor necrosis factor therapy.

BACKGROUND AND AIM: Acute severe lower gastrointestinal bleeding (LGIB) in patients with Crohn's disease (CD) is uncommon; however, it is a potentially life-threatening complication, and its recurrence is common. We thus aimed to identify the predictors for rebleeding in CD patients with acute severe LGIB and particularly focused on whether anti-tumor necrosis factor (TNF) therapy lowers the risk of rebleeding compared with conventional medical therapy (CMT) or surgery. METHODS: The risk of rebleeding was analyzed in 131 CD patients with acute severe LGIB. Patients were classified into the CMT group (n = 99), anti-TNF therapy group (n = 22), and surgery group (n = 10). No patients in the surgery group received anti-TNF therapy. RESULTS: During the median follow-up of 98 months after the first episode of acute severe LGIB, rebleeding occurred in 50.5%, 18.2%, and 30.0% of the CMT group, anti-TNF therapy group, and surgery group, respectively (P = 0.015). The cumulative risks of rebleeding at 1 and 10 years were 20.0% and 64.7% in the CMT group, 13.6% and 18.4% in the anti-TNF therapy group, and 0% and 40.7% in the surgery group, respectively (P = 0.020). Multivariable Cox regression analysis showed that anti-TNF therapy was associated with a lower risk of rebleeding compared with CMT (hazard ratio, 0.303; 95% confidence interval, 0.108-0.849; P = 0.023). CONCLUSIONS: In CD patients with acute severe LGIB, anti-TNF therapy may reduce the risk of rebleeding compared with CMT. Although surgery is considered effective in preventing early rebleeding, concomitant anti-TNF therapy may be helpful in further lowering the long-term risk of rebleeding.

Chronic Viral Hepatitis Is Associated with Colorectal Neoplasia: A Systematic Review and Meta-Analysis.

BACKGROUND: Chronic viral hepatitis is associated with a wide range of extrahepatic diseases; however, evidence on a link between chronic viral hepatitis and colorectal neoplasia is still lacking. AIMS: To analyze the association between chronic viral hepatitis and prevalence of colorectal neoplasia. METHODS: A systematic review of articles published in the MEDLINE, EMBASE, and Cochrane Library between 2000 and 2020 was performed. Subgroup analyses based on the types of colorectal neoplasia and the etiology of chronic viral hepatitis were conducted. RESULTS: Twelve eligible studies with 48,428 hepatitis B virus (HBV) patients and 46,561 hepatitis C virus (HCV) patients were included. Chronic viral hepatitis was significantly associated with an increased risk of both colorectal adenoma (odds ratio [OR], 1.53; 95% confidence interval [CI], 1.16-2.02; I2 = 83%) and colorectal cancer (CRC) (OR, 1.32; 95% CI, 1.08-1.61; I2 = 94%). The etiology of chronic viral hepatitis was an independent factor related to heterogeneity for CRC subgroup analysis revealed an increased risk of CRC in both HBV (OR, 1.18; 95% CI, 1.09-1.27; I2 = 37%) and HCV (OR, 1.88; 95% CI, 1.78-1.97; I2 = 0%). HCV was associated with an increased risk of colorectal adenoma (OR, 1.48; 95% CI, 1.22-1.79; I2 = 0%); however, HBV was not associated with an increased risk of colorectal adenoma and had considerable heterogeneity (OR, 1.65; 95% CI, 0.88-3.09; I2 = 90%). CONCLUSION: Our meta-analysis showed that chronic viral hepatitis is associated with an increased risk of colorectal neoplasia. The strategy of stricter screening colonoscopy may benefit from patients with chronic viral hepatitis.

Clinical Course of COVID-19 in Patients with Inflammatory Bowel Disease in Korea: a KASID Multicenter Study.

In 2020, the novel coronavirus disease 2019 (COVID-19) began to spread worldwide and remains an ongoing medical challenge. This case series reports on the clinical features and characteristics of patients with inflammatory bowel disease (IBD) and confirmed COVID-19 infection. From February 2020 to March 2021, nine patients with IBD had confirmed COVID-19 across four hospitals in Korea. The median age at COVID-19 diagnosis was 42 years. Six patients were male, and seven patients had ulcerative colitis (UC). No patients required oxygen therapy, intensive care unit hospitalizations, or died. The most common symptom was fever, and gastrointestinal (GI) symptoms developed as diarrhea in five patients with UC. Oral steroids were used to combat UC aggravation in two patients. In this case series of nine IBD patients diagnosed with COVID-19 in Korea, the clinical presentation was predominately a mild respiratory tract infection. Most patients with UC developed new GI symptoms including diarrhea.

Evaluation of a Concrete Slab Track with Debonding at the Interface between Track Concrete Layer and Hydraulically Stabilized Base Course Using Multi-Channel Impact-Echo Testing.

Multi-channel Impact-echo (IE) testing was used to evaluate debonding defects at the interface between track concrete layer, TCL, and hydraulically stabilized base course, HSB, in a real scale mockup model of concrete slab tracks for Korea high-speed railway (KHSR) system. The mockup model includes three debonding defects that were fabricated by inserting three 400 mm by 400 mm (length and width) thin plastic foam boards with three different thicknesses of 5 mm, 10 mm, and 15 mm, before casting concrete in TCL. Multi-channel IE signals obtained over solid concrete and debonding defects were reduced to three critical IE testing parameters (the velocity of concrete, peak frequency, and Q factor). Bilinear classification models were used to evaluate the individual and a combination of the characteristic parameters. It was demonstrated that the best evaluation performance was obtained by using average peak frequency or the combination of average peak frequency and average Q factor, obtained by eight accelerometers in the multi-channel IE device. The results and discussion in this study would improve the understanding of characteristics of multiple IE testing parameters in concrete slab tracks and provide a fundamental basis to develop an effective prediction model of non-destructive evaluation for debonding defects at the interface between TCL and HSB in concrete slab tracks.

Molecular Interaction Regulates the Performance and Longevity of Defect Passivation for Metal Halide Perovskite Solar Cells.

Defect passivation constitutes one of the most commonly used strategies to fabricate highly efficient perovskite solar cells (PSCs). However, the durability of the passivation effects under harsh operational conditions has not been extensively studied regardless of the weak and vulnerable secondary bonding between the molecular passivation agents and perovskite crystals. Here, we incorporated strategically designed passivating agents to investigate the effect of their interaction energies on the perovskite crystals and correlated these with the performance and longevity of the passivation effects. We unraveled that the passivation agents with a stronger interaction energy are advantageous not only for effective defect passivation but also to suppress defect migration. The prototypical PSCs treated with the optimal passivation agent exhibited superior performance and operational stability, retaining 81.9 and 85.3% of their initial performance under continuous illumination or nitrogen at 85 °C after 1008 h, respectively, while the reference device completely degraded during that time. This work provides important insights into designing operationally durable defect passivation agents for perovskite optoelectronic devices.

Increased intracellular Ca2+ concentrations prevent membrane localization of PH domains through the formation of Ca2+-phosphoinositides.

Insulin resistance, a key etiological factor in metabolic syndrome, is closely linked to ectopic lipid accumulation and increased intracellular Ca2+ concentrations in muscle and liver. However, the mechanism by which dysregulated intracellular Ca2+ homeostasis causes insulin resistance remains elusive. Here, we show that increased intracellular Ca2+ acts as a negative regulator of insulin signaling. Chronic intracellular Ca2+ overload in hepatocytes during obesity and hyperlipidemia attenuates the phosphorylation of protein kinase B (Akt) and its key downstream signaling molecules by inhibiting membrane localization of pleckstrin homology (PH) domains. Pharmacological approaches showed that elevated intracellular Ca2+ inhibits insulin-stimulated Akt phosphorylation and abrogates membrane localization of various PH domain proteins such as phospholipase Cδ and insulin receptor substrate 1, suggesting a common mechanism inhibiting the membrane targeting of PH domains. PH domain-lipid overlay assays confirmed that Ca2+ abolishes the binding of various PH domains to phosphoinositides (PIPs) with two adjacent phosphate groups, such as PI(3,4)P2, PI(4,5)P2, and PI(3,4,5)P3 Finally, thermodynamic analysis of the binding interaction showed that Ca2+-mediated inhibition of targeting PH domains to the membrane resulted from the tight binding of Ca2+ rather than PH domains to PIPs forming Ca2+-PIPs. Thus, Ca2+-PIPs prevent the recognition of PIPs by PH domains, potentially due to electrostatic repulsion between positively charged side chains in PH domains and the Ca2+-PIPs. Our findings provide a mechanistic link between intracellular Ca2+ dysregulation and Akt inactivation in insulin resistance.

Electrical Resistivity Measurements of Reinforced Concrete Slabs with Delamination Defects.

The main objectives of this research are to evaluate the effects of delamination defects on the measurement of electrical resistivity of reinforced concrete slabs through analytical and experimental studies in the laboratory, and to propose a practical guide for electrical resistivity measurements on concrete with delamination defects. First, a 3D finite element model was developed to simulate the variation of electric potential field in concrete over delamination defects with various depths and lateral sizes. Second, for experimental studies, two reinforced concrete slab specimens (1500 mm (width) by 1500 mm (length) by 300 mm (thickness)) with artificial delamination defects of various dimensions and depths were fabricated. Third, the electrical resistivity of concrete over delamination defects in the numerical simulation models and the two concrete slab specimens were evaluated by using a 4-point Wenner probe in accordance with AASHTO (American Association of State Highway and Transportation Office) T-358. It was demonstrated from analytical and experimental studies in this study that shallow (50 mm depth) and deep (250 mm depth) delamination defects resulted in higher and lower electrical resistivity (ER) values, respectively, as compared to measurements performed on solid concrete locations. Furthermore, the increase in size of shallow defects resulted in an increase in concrete resistivity, whereas the increase in sizes of deep delamination defects yielded opposite results. In addition, measurements done directly above the steel reinforcements significantly lowered ER values. Lastly, it was observed from experimental studies that the effect of delamination defects on the values of electrical resistivity decreases as the saturation level of concrete increases.

Vapor-Assisted Ex-Situ Doping of Carbon Nanotube toward Efficient and Stable Perovskite Solar Cells.

Single-walled carbon nanotubes (CNTs) has been considered as a promising material for a top electrode of perovskite solar cells owing to its hydrophobic nature, earth-abundance, and mechanical robustness. However, its poor conductivity, a shallow work function, and nonreflective nature have limited further enhancement in power conversion efficiency (PCE) of top CNT electrode-based perovskite solar cells. Here, we introduced a simple and scalable method to address these issues by utilizing an ex-situ vapor-assisted doping method. Trifluoromethanesulfonic acid (TFMS) vapor doping of the free-standing CNT sheet enabled tuning of conductivity and work function of the CNT electrode without damaging underneath layers. The sheet resistance of the CNT sheet was decreased by 21.3% with an increase in work function from 4.75 to 4.96 eV upon doping of TFMS. In addition, recently developed 2D perovskite-protected Cs-containing formamidium lead iodide (FACsPbI3) technology was employed to maximize the absorption. Because of the lowered resistance, better energy alignment, and improved absorption, the CNT electrode-based PSCs produced a PCE of 17.6% with a JSC of 24.21 mA/cm2, VOC of 1.005 V, and FF of 0.72. Furthermore, the resulting TFMS-doped CNT-PSCs demonstrated higher thermal and operational stability than bare CNT and metal electrode-based devices.

Controlled Redox of Lithium-Ion Endohedral Fullerene for Efficient and Stable Metal Electrode-Free Perovskite Solar Cells.

High efficiency perovskite solar cells have underpinned the rapid growth of the field. However, their low device stability limits further advancement. Hygroscopic lithium bis(trifluoromethanesulfonyl)imide (Li+TFSI-) and metal electrode are the main causes of the device instability. In this work, the redox reaction between lithium-ion endohedral fullerenes and 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobi-fluorene (spiro-MeOTAD) was controlled to optimize the amount of oxidized spiro-MeOTAD and antioxidizing neutral endohedral fullerenes. Application of this mixture to metal-free carbon nanotube (CNT)-laminated perovskite solar cells resulted in 17.2% efficiency with a stability time of more than 1100 h under severe conditions (temperature = 60 °C, humidity = 70%). Such high performance is attributed to the uninhibited charge flow, no metal-ion migration, and the enhanced antioxidizing activity of the devices.

Crystalline Liquid-like Behavior: Surface-Induced Secondary Grain Growth of Photovoltaic Perovskite Thin Film.

Surface effects usually become negligible on the micrometer or sub-micrometer scale due to lower surface-to-bulk ratio compared to nanomaterials. In lead halide perovskites, however, their "soft" nature renders them highly responsive to the external field, allowing for extended depth scale affected by the surface. Herein, by taking advantage of this unique feature of perovskites we demonstrate a methodology for property manipulation of perovskite thin films based on secondary grain growth, where tuning of the surface induces the internal property evolution of the entire perovskite film. While in conventional microelectronic techniques secondary grain growth generally involves harsh conditions such as high temperature and straining, it is easily triggered in a perovskite thin film by a simple surface post-treatment, producing enlarged grain sizes of up to 4 µm. The resulting photovoltaic devices exhibit significantly enhanced power conversion efficiency and operational stability over a course of 1000 h and an ambient shelf stability of over 4000 h while maintaining over 90% of its original efficiency.