Highly Efficient and Stable Inverted Perovskite Solar Cell Using Pure δ-FAPbI3 Single Crystals.

Pure δ-formamidinium lead triiodide (δ-FAPbI3 ) single crystal for highly efficient perovskite solar cell (PCS) with long-term stability is prepared by a new method consisting of liquid phase reaction of FAI and PbI2 in N,N-dimethyl formamide and antisolvent crystallization using acetonitrile. In this method, the incorporation of any impurity into the crystal is excluded by the molecular recognition of the crystal growth site. This pure crystal is used to fabricate α-FAPbI3 inverted PSCs which showed excellent power conversion efficiency (PCE) due to much-reduced trap-states. The champion device exhibited a high PCE of 23.48% under the 1-Sun condition. Surface-treated devices with 3-(aminomethyl)pyridine showed a significantly improved PCE of 25.07%. In addition, the unencapsulated device maintained 97.22% of its initial efficiency under continuous 1-Sun illumination for 1,000 h at 85 °C in an N2 atmosphere ensuring long-term thermal and photo stabilities of PSCs, whereas the control device kept only 89.93%.

Morphology and Performance Enhancement through the Strong Passivation Effect of Amphoteric Ions in Tin-based Perovskite Solar Cells.

Despite the optoelectronic similarities between tin and lead halide perovskites, the performance of tin-based perovskite solar cells remains far behind, with the highest reported efficiency to date being ≈14%. This is highly correlated to the instability of tin halide perovskite, as well as the rapid crystallization behavior in perovskite film formation. In this work, l-Asparagine as a zwitterion plays a dual role in controlling the nucleation/crystallization process and improving the morphology of perovskite film. Furthermore, tin perovskites with l-Asparagine show more favorable energy-level matching, enhancing the charge extraction and minimizing the charge recombination, leading to an enhanced power conversion efficiency of 13.31% (from 10.54% without l-Asparagine) with remarkable stability. These results are also in good agreement with the density functional theory calculations. This work not only provides a facile and efficient approach to controlling the crystallization and morphology of perovskite film but also offers guidelines for further improved performance of tin-based perovskite electronic devices.

Long-term mortality in patients with moyamoya angiopathy according to stroke presentation type in South Korea.

BACKGROUND: Incidence, prevalence, and long-term survival outcomes in patients with moyamoya angiopathy (MMA) according to stroke presentation type and age group have not been clearly elucidated. METHODS: We investigated mortality in patients with MMA (moyamoya disease, probable moyamoya disease, moyamoya syndrome) of whose International Classification Disease 10 code was I67.5 from 2006 to 2015 using the Korean National Health Insurance database. MMA at diagnosis was classified into 3 types (ischemic, hemorrhagic, and asymptomatic or else) according to stroke presentation. Survival analysis was performed according to stroke presentation type and age group (< 15 years and ≥ 15 years) using the Kaplan-Meier method. RESULTS: There were 12,146 newly diagnosed moyamoya cases, with a female-to-male ratio of 1.81; the ischemic type was identified in 3671 (30.2%) patients, the hemorrhagic type in 2449 (20.2%) patients, and the asymptomatic or else type in 6026 (49.6%) patients. The mean age at diagnosis according to stroke presentation was 33.1 (± 14.8) years in asymptomatic or else type, 41.2 (± 17.3) years in ischemic type, and 45.4 (± 14.3) years in hemorrhagic type (P < 0.001). The 10-year survival rates in ischemic-, hemorrhagic-, and asymptomatic or else-type patients were 88.9%, 76.3%, and 94.3%, respectively (log-rank test; P < 0.001). Pediatric MMA (< 15 years) and adult MMA (≥ 15 years) showed different survival curves according to stroke presentation type (log-rank test; P = 0.017, P < 0.001, respectively). CONCLUSIONS: Our study showed that moyamoya patients had different diagnosis ages and distinct survival courses according to stroke presentation type. Adult moyamoya patients with hemorrhagic presentation had the worst survival outcomes.

Synthesis of Single-Crystalline Hexagonal Graphene Quantum Dots from Solution Chemistry.

Graphene-based carbon nanostructures with nanometer dimensions have been of great interest due to the existence of a bandgap. So far, well-ordered edge structure and uniformly synthesized graphene quantum dots (GQDs) with a hexagonal single-crystalline structure have not been directly observed owing to the limited precision of current synthesis approaches. Herein, we report on a novel approach not just for the synthesis of the size-controlled single-crystalline GQDs with hexagonal shape but also for a new discovery on constructing 2D and 3D graphene single crystal structures from d-glucose via catalytic solution chemistry. With size-controlled single-crystalline GQDs, we elucidated the crucial role of edge states on luminescence from the correlation between their crystalline size and exciton lifetime. Furthermore, blue-emissive single-crystalline GQDs were used as an emitter on light-emitting diodes and exhibit stable deep-blue emission regardless of the voltage and doping level.

Uniform Ag Nanocubes Prepared by AgCl Particle-Mediated Heterogeneous Nucleation and Disassembly and Their Mechanism Study by DFT Calculation.

Uniform Ag nanocubes are reproducibly synthesized by a AgCl particle-mediated heterogeneous nucleation and disassembly process in polyol chemistry. By introducing N,N-dimethylformamide (DMF) in a conventional polyol method with HCl etchant, Ag nanocrystals (NCs) begin to be nucleated on the surface of AgCl-precipitated particles due to the promoted reduction reaction by DMF. The nucleated Ag NCs on the AgCl particles are grown to Ag nanocubes in shape by consuming Ag sources from the AgCl mother particles. Eventually the grown Ag nanocubes are disassembled from the mother AgCl particles because the AgCl particles are fully digested by the growing Ag nanocubes. Density functional theory calculation confirms that the Ag atoms can be favorably deposited on the (100) facet of AgCl particles and the Ag nuclei on the AgCl particles tend to reveal (100) facet.

Direct measurement of electrostatic interactions between poly(methyl methacrylate) microspheres with optical laser tweezers.

In this study, we measured the force of electrostatic interactions between poly(methyl methacrylate) (PMMA) particles dispersed in organic solvent mixtures of cyclohexyl bromide (CHB) and n-decane. Optical laser tweezers were employed to directly measure interactive forces between paired PMMA particles in a CHB medium that contained n-decane in various volume ratios. CHB, having a moderate dielectric constant, provided an environment with a high charge storage capacity. The addition of n-decane lowered the effective refractive index of the medium, which increased the optical trapping efficiency. We also fabricated microscope flow cells with a commonly used UV-curable adhesive and quantified the effects of dissolved adhesive compounds through interactive force measurements and nuclear magnetic resonance analysis. In addition, we studied the impact of CHB dissociation into H+ and Br- ions, which could screen electrostatic interactions.

Heterogeneous Capillary Interactions of Interface-Trapped Ellipsoid Particles Using the Trap-Release Method.

Heterogeneous capillary interactions between ellipsoid particles at the oil-water interface were measured via optical laser tweezers. Two trapped particles were aligned in either tip-to-tip (tt) or side-to-side (ss) configurations via the double-trap method and were released from the optical traps, leading to particle-particle attractions due to the capillary forces caused by quadrupolar interface deformation. On the basis of image analysis and calculations of the Stokes drag force, the capillary interactions between two ellipsoid particles with the same aspect ratio (E) were found to vary with the particle pairs that were measured, indicating that the interactions were nondeterministic or heterogeneous. Heterogeneous capillary interactions could be attributed to undulation of the interface meniscus due to chemical and/or geometric particle heterogeneity. The power law exponent for the capillary interaction Ucap ≈ r-ß was found to be ß ≈ 4 and was independent of the aspect ratio and particle configuration in long-range separations. Additionally, with regard to the tt configuration, the magnitude of the capillary force proportionally increased with the E value (E > 1) when two ellipsoid particles approached each other in the tt configuration.

Three-Dimensional Structures Based on the Fusion of Chrysene and Spirobifluorene Chromophores for the Development of Blue OLEDs.

A new deep-blue chromophore containing a three-dimensionally (3D) shaped CS core composed of fused chrysene and spirofluorene units is synthesized. A pair of m-terphenyl (TP) units is also substituted onto the CS core at two different sets of positions to form two additional compounds: CS-TPTP and TP-CS-TP. The TP-CS-TP compound showed the highest efficiency with an external quantum efficiency (EQE) of 3.05% and Commission Internationale de L'Eclairage coordinates (CIE) of (0.148, 0.098) corresponding to the emission of blue light. This approach for forming a new chromophore is expected to lead to the development of functional organic materials with excellent characteristics.

Growth of Silver Nanowires from Controlled Silver Chloride Seeds and Their Application for Fluorescence Enhancement Based on Localized Surface Plasmon Resonance.

A "Polyol" method has granted low-cost and facile process-controllability for silver-nanowire (Ag-NW) synthesis. Although homogenous and heterogeneous nucleation and growth during Ag-NW synthesis are possible using polyol methods, heterogeneous nucleation and growth of Ag NW guarantees highly selective growth of nanostructures using silver chloride (AgCl) seeds, which provides a stable source of chloride ions (Cl-) and thermodynamic reversibility. In this paper, a microdroplet has been adopted to synthesize uniform AgCl seeds with different diameter that are used for seed-mediated Ag-NW synthesis. The concentration of two precursors (AgNO3 and NaCl) in the droplets is modulated to produce different sizes of AgCl seeds, which determines the diameter and length of Ag NWs. The process of the seed-mediated growth of Ag NWs has been monitored by observing the peak shift in the time-resolved UV-vis extinction spectrum. Furthermore, the distinct plasmonic property of Ag NWs for transverse and longitudinal localized-surface-plasmon-resonance (LSPR)-mediated fluorescence enhancement is utilized. The high aspect ratio and sharp tips work as simple antennas that induce the enhanced fluorescence emission intensity of a fluorophore, which can be applied in the fields of biological tissue imaging and therapy.

Uniform Microgels Containing Agglomerates of Silver Nanocubes for Molecular Size-Selectivity and High SERS Activity.

Surface-enhanced Raman scattering (SERS) is a promising technique for molecular analysis as the molecular fingerprints (Raman spectra) are amplified to detectable levels compared with common spectroscopy. Metal nanostructures localize electromagnetic field on their surfaces, which can lead to dramatic increase of Raman intensity of molecules adsorbed. However, the metal surfaces are prone to contamination, thereby requiring pretreatment of samples to remove adhesive molecules. To avoid the pretreatment and potentially achieve point-of-care (POC) analysis, we have developed SERS-active microgels using the droplet-microfluidic system. As the microgels are composed of water-swollen network with consistent mesh size, they selectively allow diffusion of molecules smaller than the mesh, thereby excluding large adhesives. To render the microgels highly SERS-active, we destabilize silver nanocubes to form agglomerates, which are embedded in the matrix of microgels. The nanogaps in the agglomerates provide high sensitivity in Raman measurement and size-selective permeability of the microgel matrix obviates the pretreatment of samples. To validate the functions, we demonstrate the direct detection of Aspirin dissolved in whole blood without any pretreatment.

Electrostatic interactions between particles through heterogeneous fluid phases.

We investigated the electrostatic interactions between particles acting through heterogeneous fluid phases. An oil lens system floating on the surface of water was used to trap particles at different fluid-fluid interfaces. The inner particles are located at the centrosymmetrically curved oil-water interface inside the oil lens while satellite particles are located at the curved air-water interface, separated by a particular distance from the triple phase boundary. The satellite particles are likely to be captured in an energy minimum state due to electrostatic repulsions by the inner particles balanced with the gravity-induced potential energy. As the size of the oil lens decreases upon evaporation, the satellite particles escape from the gravitational confinement at a critical moment. The self-potential values of the inner particles and the satellite particles were calculated by employing an energy balance and the experimentally obtained geometric parameter values. It was found that the self-potential values of the inner particles decrease as oil evaporates over time and that the magnitude of the self-potential of the satellite particles is a hundred times larger than that of the inner particles. These results demonstrate significant effects of the thickness and shape of the nonpolar superphase on the electrostatic interactions between the particles trapped at different fluid-fluid interfaces.

Occupational blood exposures in health care workers: incidence, characteristics, and transmission of bloodborne pathogens in South Korea.

BACKGROUND: Health care workers (HCWs) are at high risk for occupational blood exposures (OBEs) and transmission of bloodborne pathogens. This study elucidated the incidence rate and epidemiological characteristics of OBEs among HCWs and investigated the pathogen transmission rate for hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV). METHODS: Self-reported OBEs from January 1, 2011 to December 31, 2015 were obtained from the electronic recording system. OBE incidence densities per 100 person-years and per 100 bed-years were calculated with a 5-year trend analysis. OBE characteristics and pathogen transmission rates were evaluated. RESULTS: Among 10,452 HCWs and 1072 average yearly beds, 1076 OBEs were reported. OBE incidence rate was 5.6 cases per 100 person (full-time equivalent)-years and 20.3 per 100 bed-years. Incidence rate decreased and was significantly associated with a decrease of beds served per HCW. Housekeeping showed the highest OBE rate (14.8%) followed by doctors (8.5%) and nurses (6.2%). OBEs occurred in wards, emergency rooms, and operating rooms (38.1%, 13.3% and 12.2%, respectively) via percutaneous (86.7%) and mucocutaneous exposures (13.2%). Of OBEs associated with HBV (n = 133), HCV (n = 126), and HIV (n = 25), only one led to an infection (HCV; transmission rate of 0.8%). Neither HBV nor HIV infection occurred. CONCLUSIONS: OBE incidence rate in a Korean university hospital was 5.6 cases per 100 person-years and 20.3 per 100 bed-years and was related to HCW workload and work proficiency. Though the actual bloodborne pathogen transmission rate was low, efforts to prevent OBE should be made for hospital safety.

Efficient hysteresis-less bilayer type CH3NH3PbI3 perovskite hybrid solar cells.

Bilayer type CH3NH3PbI3 (MAPbI3) perovskite hybrid solar cells were fabricated via a one-step spin-coating process by using solubility controlled MAPbI3 solutions of MAPbI3-DMSO (dimethyl sulfoxide) and MAPbI3-DMF (N, N-dimethylformamide)-HI. The best DMSO-bilayer device showed 1.07 ± 0.02 V V(oc) (open-circuit voltage), 20.2 ± 0.1 mA cm(-2) J(sc) (short-circuit current density), 68 ± 2% FF (fill factor), and 15.2 ± 0.3% η (overall power conversion efficiency) under the forward scan direction and 1.07 ± 0.02 V V(oc), 20.4 ± 0.1 mA cm(-2) J(sc), 70 ± 3% FF, and 15.9 ± 0.4% η under the reverse scan direction. The best HI-bilayer device had 1.08 ± 0.02 V V(oc), 20.6 ± 0.1 mA cm(-2) J(sc), 75 ± 1% FF, and 17.2 ± 0.2% η under the forward scan direction and 1.08 ± 0.02 V V(oc), 20.6 ± 0.1 mA cm(-2) J(sc), 76 ± 2% FF, and 17.4 ± 0.3% η under the reverse scan direction. The deviation of average device efficiency (η(avg)) of 20 DMSO samples and 20 HI samples was 14.2 ± 0.95% and 16.2 ± 0.85%, respectively. Therefore, the HI-bilayer devices exhibited better device efficiency and smaller J-V (current density-voltage) hysteresis with respect to the scan direction than the DMSO-bilayer devices due to the reduced recombination and traps by the formation of a purer and larger MAPbI3 perovskite crystalline film.

Long-term results of motor cortex stimulation in the treatment of chronic, intractable neuropathic pain.

BACKGROUND/OBJECTIVES: Although motor cortex stimulation (MCS) has been used for more than 20 years in the treatment of chronic neuropathic pain, there is still a debate about the efficacy of MCS. METHODS: To investigate the long-term results and the factors associated with the long-term success of chronic MCS, 21 patients who underwent MCS trial were classified as having central poststroke pain, central pain after spinal cord injury (SCI) and peripheral neuropathic pain, and we investigated the clinical factors associated with long-term success and degree of pain relief. RESULTS: Of the 21 patients, 16 (76.2%) had a successful trial and underwent chronic MCS. In the long-term follow-up (53 ± 39 months), only the diagnosis (central poststroke pain and peripheral neuropathic pain) was associated with long-term success defined as >30% pain relief compared with baseline (p < 0.05, χ(2) test). The difference in pain relief was not significant in patients having SCI pain (p > 0.05, 1-way ANOVA). The other variables did not show any significant influence in the long-term success and degree of pain relief (p > 0.05, 1-way ANOVA). CONCLUSIONS: MCS was more effective in the treatment of chronic neuropathic pain of central poststroke pain and peripheral neuropathic pain types than in the treatment of SCI pain in the long-term follow-up.

Chemical management for colorful, efficient, and stable inorganic-organic hybrid nanostructured solar cells.

Chemically tuned inorganic-organic hybrid materials, based on CH3NH3(═MA)Pb(I(1-x)Br(x))3 perovskites, have been studied using UV-vis absorption and X-ray diffraction patterns and applied to nanostructured solar cells. The band gap engineering brought about by the chemical management of MAPb(I(1-x)Br(x))3 perovskites can be controllably tuned to cover almost the entire visible spectrum, enabling the realization of colorful solar cells. We demonstrate highly efficient solar cells exhibiting 12.3% in a power conversion efficiency of under standard AM 1.5, for the most efficient device, as a result of tunable composition for the light harvester in conjunction with a mesoporous TiO2 film and a hole conducting polymer. We believe that the works highlighted in this paper represent one step toward the realization of low-cost, high-efficiency, and long-term stability with colorful solar cells.

Sb(2)Se(3) -sensitized inorganic-organic heterojunction solar cells fabricated using a single-source precursor.

The photovoltaic performance of Sb2 Se3 -sensitized heterojunction solar cells, which were fabricated by a simple deposition of Sb2 Se3 on mesoporous TiO2 by an approach that features multiple cycles of spin coating with a single-source precursor solution and thermal decomposition, is reported. Poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothioadiazole)] was used as the hole-transporting material. The most efficient cell exhibited a short-circuit current density of 22.3 mA cm(-2) , an open-circuit voltage of 304.5 mV, and a fill factor of 47.2 %, yielding a power conversion efficiency of 3.21 % under standard test conditions (irradiation of 1000 W m(-2) , air mass=1.5 G). The results of this study imply that the developed approach has a high potential as a simple and effective route for the fabrication of efficient and inexpensive solar cells.

Proper Indication of Decompressive Craniectomy for the Patients with Massive Brain Edema after Intra-arterial Thrombectomy.

OBJECTIVE: Numerous studies have indicated that early decompressive craniectomy (DC) for patients with major infarction can be life-saving and enhance neurological outcomes. However, most of these studies were conducted by neurologists before the advent of intra-arterial thrombectomy (IA-Tx). This study aims to determine whether neurological status significantly impacts the final clinical outcome of patients who underwent DC following IA-Tx in major infarction. METHODS: This analysis included 67 patients with major anterior circulation major infarction who underwent DC after IA-Tx, with or without intravenous tissue plasminogen activator. We retrospectively reviewed the medical records, radiological findings, and compared the neurological outcomes based on the "surgical time window" and neurological status at the time of surgery. RESULTS: For patients treated with DC following IA-Tx, a Glasgow coma scale (GCS) score of 7 was the lowest score correlated with a favorable outcome (p=0.013). Favorable outcomes were significantly associated with successful recanalization after IA-Tx (p=0.001) and perfusion/diffusion (P/D)-mismatch evident on magnetic resonance imaging performed immediately prior to IA-Tx (p=0.007). However, the surgical time window (within 36 hours, p=0.389; within 48 hours, p=0.283) did not correlate with neurological outcomes. CONCLUSION: To date, early DC surgery after major infarction is crucial for patient outcomes. However, this study suggests that the indication for DC following IA-Tx should include neurological status (GCS ≤7), as some patients treated with early DC without considering the neurological status may undergo unnecessary surgery. Recanalization of the occluded vessel and P/D-mismatch are important for long-term neurological outcomes.

Comparative Analysis of Balloon Angioplasty Alone versus Carotid Artery Stenting for Severe Extracranial Carotid Artery Stenosis: A 4-Year Retrospective Study.

BACKGROUND: This retrospective study aimed to compare the efficacy of balloon angioplasty alone (BAA) with carotid artery stenting (CAS) for severe extracranial carotid artery stenosis. The primary outcomes assessed were restenosis requiring retreatment and symptomatic stroke occurrence within a 4-year follow-up period. METHODS: A total of 77 patients with 89 carotid artery stenoses undergoing endovascular carotid revascularization between January 2015 and December 2019 were included. Neuroradiologic evaluations, including computed tomography angiography or magnetic resonance angiography, were performed at defined intervals. Statistical analyses were conducted to compare patient characteristics, angiographic outcomes, and clinical outcomes between the BAA and CAS groups. RESULTS: The study demonstrated successful outcomes in both groups with low adverse event rates. The overall restenosis rate was 40.2%, but severe restenosis requiring retreatment occurred in only 10 cases (7 in BAA, and 3 in CAS). No significant difference was found in retreatment rates between the 2 groups (P = 0.53). Stroke occurrence within the 4-year follow-up period was observed in 3 patients, with no statistically significant difference between BAA and CAS groups. CONCLUSIONS: This study provides valuable insights into the comparative effectiveness of BAA and CAS for severe extracranial carotid artery stenosis. Despite slightly shorter intervals to restenosis in the BAA group, there was no significant difference in retreatment or stroke occurrence rates between the 2 procedures. BAA offers advantages in terms of retreatment options.

Inorganic-Derived 0D Perovskite Induced Surface Lattice Arrangement for Efficient and Stable All-Inorganic Perovskite Solar Cells.

The inverted inorganic CsPbI3 perovskite solar cells (PSCs) are prospective candidates for next-generation photovoltaics owing to inherent robust thermal/photo-stability and compatibility for tandems. However, the performance and stability of the inverted CsPbI3 PSCs fall behind the n-i-p counterparts due to poor energetic alignment and abundant interfacial defect states. Here, an inorganic 0D Cs4PbBr6 with a good lattice strain arrangement is implemented as the surface anchoring capping layer on CsPbI3. The Cs4PbBr6 perovskite induces enhanced electron-selective junction and thus facilitates efficient charge extraction and effectively inhibits non-radiative recombination. Consequently, the CsPbI3 PSCs with Cs4PbBr6 demonstrate the highest power conversion efficiency (PCE) of CsPbI3-based inverted PSCs, reaching 21.03% PCE from a unit cell and 17.39% PCE from a module with a 64 cm2 aperture area. Furthermore, the resulting devices retain 92.48% after 1000 h under simultaneous 1-sun and damp heat (85 °C / 85% relative humidity) environment.