•This study verified the applicability of DED to repair of damaged PBF parts.•Hot-rolled and PBF specimens with trapezoidal grooves were repaired through filling the grooves using DED.•The ...microstructure of the repaired area was mainly composed of complicated dendrite structures.•Interfacial cracks occurred around the repaired zone for specimens with large groove depths.•The degradation in tensile properties was within 5% for repaired specimen with 0.5 mm depth.
Powder bed fusion (PBF), a 3D printing process, is widely used for manufacturing 316L stainless steel parts. When these PBF parts are damaged or worn severely during service, they can be repaired by conventional repair processes such as GTAW welding, metal spraying, brazing etc. However, these processes have several disadvantages such as creating a large heat affected zone and repair defects (pores and cracks). In contrast, directed energy deposition (DED) provides good metallurgical bonds, minimal dilution, and a small heat-affected zone. In this study, to verify the applicability of DED to repair of damaged PBF parts, we repaired sample parts and observed their tensile properties, hardness, and metallurgical characteristics. First, we designed hot-rolled and PBF specimens with trapezoidal grooves of varying depth. After filling the groove using DED, the specimens were tested for tensile properties. We found that in specimens with large groove depths (1 mm and 2 mm), cracks occurred around the repair due to thermal stresses and oxide inclusion. For this reason, strength and elongation were lower in these specimens. We also found that the micro-hardness of the deposition zone is greater than the original hot-rolled specimens and similar to the PBF specimens. The microstructure of the repaired area is mainly composed of complicated dendrite structures due to irregular nucleation. In addition, dimples were observed in the fracture surfaces, indicating that ductile fracture occurred. We conclude that the DED process can be employed to repair damaged 316L stainless steel parts, with the low severity of the damage to be repaired.
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Metabolic dysfunction-associated fatty liver disease (MAFLD) is a chronic condition characterized by hepatic fat accumulation combined with underlying metabolic dysregulation. Having evolved from the ...previous term of nonalcoholic fatty liver disease (NAFLD), the term MAFLD more closely implicates the presence of overweight/obesity, type 2 diabetes, or metabolic dysregulation as essential pathogenic factors, leading to better identification of individuals with this metabolic liver disease. Low-grade inflammation, increased oxidative stress, mitochondrial dysfunction, and intestinal dysbiosis are also involved in its pathogenesis. MAFLD is not only associated with liver-related complications, but also with adverse cardiometabolic outcomes. Further studies are needed to assess whether the newly proposed definition of MAFLD is more accurate than the NAFLD in predicting the adverse liver-related and extrahepatic outcomes.
The term ‘nonalcoholic fatty liver disease’ (NAFLD) has several drawbacks; namely, an ambiguous overlap between simple steatosis and nonalcoholic steatohepatitis, and heterogeneity in interactions with other risk factors, making it difficult to predict its clinical effects.The new descriptor ‘metabolic dysfunction-associated fatty liver disease’ (MAFLD) is proposed to replace the term NAFLD, because it more closely implicates obesity and metabolic dysregulation, leading to better identification of individuals with metabolic liver disease.Metaflammation, oxidative stress, mitochondrial dysfunction, sarcopenia, and intestinal dysbiosis are also critically involved in the pathogenesis of MAFLD.To apply the term MAFLD in clinical practice, many challenging questions should be addressed in a holistic way through international cooperation between relevant medical specialists.Further research is needed to establish whether, and how, the proposed change to MAFLD impacts the risk of adverse hepatic and extrahepatic clinical outcomes.
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Since the first report on the long-term durable 9.7% solid-state perovskite solar cell employing methylammonium lead iodide (CH3NH3PbI3), mesoporous TiO2, and ...2,2′,7,7′-tetrakisN,N-di(4-methoxyphenyl)amino-9,9′-spirobifluorene (spiro-MeOTAD) in 2012, following the seed technologies on perovskite-sensitized liquid junction solar cells in 2009 and 2011, a surge of interest has been focused on perovskite solar cells due to superb photovoltaic performance and extremely facile fabrication processes. The power conversion efficiency (PCE) of perovskite solar cells reached 21% in a very short period of time. Such an unprecedentedly high photovoltaic performance is due to the intrinsic optoelectronic property of organolead iodide perovskite material. Moreover, a high dielectric constant, sub-millimeter scale carrier diffusion length, an underlying ferroelectric property, and ion migration behavior can make organolead halide perovskites suitable for multifunctionality. Thus, besides solar cell applications, perovskite material has recently been applied to a variety fields of materials science such as photodetectors, light emitting diodes, lasing, X-ray imaging, resistive memory, and water splitting. Regardless of application areas, the growth of a well-defined perovskite layer with high crystallinity is essential for effective utilization of its excellent physicochemical properties. Therefore, an effective methodology for preparation of high quality perovskite layers is required. In this Account, an effective methodology for production of high quality perovskite layers is described, which is the Lewis acid–base adduct approach. In the solution process to form the perovskite layer, the key chemicals of CH3NH3I (or HC(NH2)2I) and PbI2 are used by dissolving them in polar aprotic solvents. Since polar aprotic solvents bear oxygen, sulfur, or nitrogen, they can act as a Lewis base. In addition, the main group compound PbI2 is known to be a Lewis acid. Thus, PbI2 has a chance to form an adduct by reacting with the Lewis base. Crystal growth and morphology of perovskite can be controlled by taking advantage of the weak chemical interaction in the adduct. We have successfully fabricated highly reproducible CH3NH3PbI3 perovskite solar cells with PCE as high as 19.7% via adducts of PbI2 with oxygen-donor N,N′-dimethyl sulfoxide. This adduct approach has been found to be generally adopted, where formamidinium lead iodide perovskite, HC(NH2)2PbI3 (FAPbI3), with large grain, high crystallinity, and long-lived carrier lifetime was successfully fabricated via an adduct of PbI2 with sulfur-donor thiourea as Lewis base. The adduct approach proposed in this Account is a very promising methodology to achieve high quality perovskite films with high photovoltaic performance. Furthermore, single crystal growth on the conductive substrate is expected to be possible if we kinetically control the elimination of Lewis base in the adduct.
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Although power conversion efficiency (PCE) of state‐of‐the‐art perovskite solar cells has already exceeded 20%, photo‐ and/or moisture instability of organolead halide perovskite have prevented ...further commercialization. In particular, the underlying weak interaction of organic cations with surrounding iodides due to eight equivalent orientations of the organic cation along the body diagonals in unit cell and chemically non‐inertness of organic cation result in photo‐ and moisture instability of organometal halide perovskite. Here, a perovskite light absorber incorporating organic–inorganic hybrid cation in the A‐site of 3D APbI3 structure with enhanced photo‐ and moisture stability is reported. A partial substitution of Cs+ for HC(NH2)2+ in HC(NH2)2PbI3 perovskite is found to substantially improve photo‐ and moisture stability along with photovoltaic performance. When 10% of HC(NH2)2+ is replaced by Cs+, photo‐ and moisture stability of perovskite film are significantly improved, which is attributed to the enhanced interaction between HC(NH2)2+ and iodide due to contraction of cubo‐octahedral volume. Moreover, trap density is reduced by one order of magnitude upon incorporation of Cs+, which is responsible for the increased open‐circuit voltage and fill factor, eventually leading to enhancement of average PCE from 14.9% to 16.5%.
FA0.9Cs0.1PbI3 with improved moisture‐ and photostability is developed. Incorporation of 10% of Cs cation in the FA cation sites improves photovoltaic performance as well as photo‐ and moisture stability. Property–structure correlation plays important role in improving the stability of perovskite solar cells.
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5.
High-Efficiency Perovskite Solar Cells Kim, Jin Young; Lee, Jin-Wook; Jung, Hyun Suk ...
Chemical reviews,
08/2020, Volume:
120, Issue:
15
Journal Article
Peer reviewed
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.
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An extremely high degree of circularly polarized photoluminescence (CPPL) and electroluminescence (CPEL) (dissymmetry factor values: |gPL| = 0.72 and |gEL| = 1.13) are generated from twisted stacking ...of achiral conjugated polymer induced by nonemitting chiral dopant of high helical twisting power for the first time. Using a theoretical analysis incorporating the Stokes parameter, the twisting angle and birefringence of the aligned conjugated polymer, and the degree of linear polarization in the emitted light are found to make a roughly equal contribution to the degree of CPEL as to the degree of CPPL. Moreover, it is also found that the location of the recombination zone within the emitting layer is a crucial parameter for determining the difference in the dissymmetry factor between CPEL and CPPL. This result is applied to an organic light‐emitting display to improve the luminous efficiency by 60%.
Highly circularly polarized electroluminescence (|gEL| = 1.13) is generated from twisted stacking of achiral conjugated polymer induced by nonemitting chiral dopant of high helical twisting power. The location of the recombination zone is a crucial parameter for determining the degree of circular polarization. The result is applied to an organic light‐emitting display to improve the luminous efficiency by 60%.
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For resolving toxicity issues of Pb‐based perovskites, Sn‐based perovskites have been widely studied as a promising alternative due to similar valence electron configuration between Sn2+ and Pb2+. ...However, desired Sn2+ in the precursor solution and film is easily oxidized to Sn4+, causing detrimental Sn vacancies and impurities in the films. Unfortunately, dimethyl sulfoxide, a ubiquitously used Lewis base for the fabrication of high‐quality perovskite thin films via the adduct approach, further accelerates the oxidation of Sn2+ in the precursor solution. Herein, N,N′‐dimethylpropyleneurea (DMPU) is proposed as an alternative Lewis base for the fabrication of high‐quality Sn‐based perovskite thin films. The strongly coordinating Lewis base DMPU is shown to suppress the oxidation of Sn2+ in the precursor solution while promoting growth of uniform and highly crystalline thin films. The PEA2SnI4 perovskite light emitting diode (PeLED) based on DMPU demonstrates dramatically improves luminance (L): a more than sixfold enhanced external quantum efficiency (EQE) and better operational stability than those of the device fabricated without DMPU. The optimum PeLED based on DMPU achieves a maximum L and EQE of 68.84 cd m−2 and 0.361%, respectively. This study provides an important methodological base for studying Sn perovskites for development of high‐performance and eco‐friendly PeLEDs.
By adopting Lewis bases with varying coordinating ability, interplays between the coordinating ability of the Lewis base and tin halide perovskite film quality is unraveled. The strongly coordinating N,N′‐dimethylpropyleneurea suppresses oxidation of Sn2+ in the precursor solution while promoting growth of uniform and highly crystalline Sn perovskite thin films for achieving high‐performance lead‐free perovskite light emitting diodes.
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The transcription factor JUN is highly expressed in pulmonary fibrosis. Its induction in mice drives lung fibrosis, which is abrogated by administration of anti-CD47. Here, we use high-dimensional ...mass cytometry to profile protein expression and secretome of cells from patients with pulmonary fibrosis. We show that JUN is activated in fibrotic fibroblasts that expressed increased CD47 and PD-L1. Using ATAC-seq and ChIP-seq, we found that activation of JUN rendered promoters and enhancers of CD47 and PD-L1 accessible. We further detect increased IL-6 that amplified JUN-mediated CD47 enhancer activity and protein expression. Using an in vivo mouse model of fibrosis, we found two distinct mechanisms by which blocking IL-6, CD47 and PD-L1 reversed fibrosis, by increasing phagocytosis of profibrotic fibroblasts and by eliminating suppressive effects on adaptive immunity. Our results identify specific immune mechanisms that promote fibrosis and suggest a therapeutic approach that could be used alongside conventional anti-fibrotics for pulmonary fibrosis.
Anomalous current–voltage (J–V) hysteresis in perovskite (PSK) solar cell is open to dispute, where hysteresis is argued to be due to electrode polarization, dipolar polarization, and/or native ...defects. However, a correlation between those factors and J–V hysteresis is hard to be directly evaluated because they usually coexist and are significantly varied depending on morphology and crystallinity of the PSK layer, selective contacts, and device architecture. In this study, without changing morphology and crystallinity of PSK layer in a planar heterojunction structure employing FA0.9Cs0.1PbI3, a correlation between J–V hysteresis and trap density is directly evaluated by means of thermally induced PbI2 regulating trap density. Increase in thermal annealing time at a given temperature of 150 °C induces growth of PbI2 on the PSK grain surface, which results in significant reduction of nonradiative recombination. Hysteresis index is reduced from 0.384 to 0.146 as the annealing time is increased from 5 to 100 min due to decrease in the amplitude of trap-mediated recombination. Reduction of hysteresis by minimizing trap density via controlling thermal annealing time leads to the stabilized PCE of 18.84% from the normal planar structured FA0.9Cs0.1PbI3 PSK solar cell.
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We report a highly efficient solar cell based on a submicrometer (∼0.6 μm) rutile TiO2 nanorod sensitized with CH3NH3PbI3 perovskite nanodots. Rutile nanorods were grown hydrothermally and their ...lengths were varied through the control of the reaction time. Infiltration of spiro-MeOTAD hole transport material into the perovskite-sensitized nanorod films demonstrated photocurrent density of 15.6 mA/cm2, voltage of 955 mV, and fill factor of 0.63, leading to a power conversion efficiency (PCE) of 9.4% under the simulated AM 1.5G one sun illumination. Photovoltaic performance was significantly dependent on the length of the nanorods, where both photocurrent and voltage decreased with increasing nanorod lengths. A continuous drop of voltage with increasing nanorod length correlated with charge generation efficiency rather than recombination kinetics with impedance spectroscopic characterization displaying similar recombination regardless of the nanorod length.
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