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BackgroundRecent studies have reported the preventive effects of probiotics on obesity. Among commensal bacteria, bifidobacteria is one of the most numerous probiotics in the mammalian gut and are a type of lactic acid bacteria. The aim of this study was to assess the antiobesity and lipid-lowering effects of Bifidobacterium spp. isolated from healthy Korean on high fat diet-induced obese rats.MethodsThirty-six male Sprague-Dawley rats were divided into three groups as follows: (1) SD group, fed standard diet; (2) HFD group, fed high fat diet; and (3) HFD-LAB group, fed high fat diet supplemented with LAB supplement (B. pseudocatenulatum SPM 1204, B. longum SPM 1205, and B. longum SPM 1207; 108 ~ 109 CFU). After 7 weeks, the body, organ, and fat weights, food intake, blood serum levels, fecal LAB counts, and harmful enzyme activities were measured.ResultsAdministration of LAB reduced body and fat weights, blood serum levels (TC, HDL-C, LDL-C, triglyceride, glucose, leptin, AST, ALT, and lipase levels), and harmful enzyme activities (β-glucosidase, β-glucuronidase, and tryptophanase), and significantly increased fecal LAB counts.ConclusionThese data suggest that Bifidobacterium spp. used in this study may have beneficial antiobesity effects.

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 FACsPbI, a correlation between J-V hysteresis and trap density is directly evaluated by means of thermally induced PbI regulating trap density. Increase in thermal annealing time at a given temperature of 150 °C induces growth of PbI 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 FACsPbI PSK solar cell.

For scalable perovskite solar cells (PSCs), deposition of a homogeneous and high-quality perovskite film on a large area (>100 cm 2 ) is a prerequisite. Conventional solutions for spin-coating on small areas usually contain polar aprotic solvents with high boiling point, which is difficult to adopt for large-area bar coating because of the uncontrollable and slow drying process due to the strong interaction between polar aprotic solvent and Lewis acidic PbI 2 or perovskite. Thus, the precursor solution plays a vital role in the success of largearea coating. Here we report a coating solution suitable for large-area perovskite films. The coating solutions prepared via gas-mediated solid−liquid conversion contain preformed perovskite clusters as confirmed by rotational mode of methylammonium cation in the PbI 3 − framework from Raman spectroscopy. CH 3 NH 3 PbI 3 (MAPbI 3 ) films formed by D-bar coating within 20 s on the area over 100 cm 2 exhibit tetragonal/cubic superlattice structure with highly preferred orientation in the entire film, which results in average power conversion efficiency (PCE) of 17.01% and best PCE of 17.82%.

Here, we report on precursor engineering for a large-area perovskite film using an air-knife-assisted D-bar coater. Lead acetate (PbAc2) is stoichiometrically added in the mother solution consisting of methylammonium iodide (MAI) and lead iodide (PbI2) in 2-methoxyethanol (2ME), leading to MAPbI3 and byproduct methylammonium acetate (MAAc). Crystal growth can be controlled in the presence of MAAc while drying the wet film. An average power conversion efficiency (PCE) of 15.14% is achieved, whereas the quality of the perovskite film is uncontrollable in the absence of PbAc2, resulting in a PCE as low as 2.63%. Carrier lifetime is further improved by about 46% when incorporating 0.12 mol % guanidinium iodide (GAI) in the PbAc2-containing precursor solution, which demonstrates a PCE of 19.44% with a device employing a piece of the large-area perovskite film (∼46 cm2) and a PCE of 13.85% with a module with an active area of 16 cm2.

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With the impressive record power conversion efficiency (PCE) of perovskite solar cells exceeding 23%, research focus now shifts onto issues closely related to commercialization. One of the critical hurdles is to minimize the cell-to-module PCE loss while the device is being developed on a large scale. Since a solution-based spin-coating process is limited to scalability, establishment of a scalable deposition process of perovskite layers is a prerequisite for large-area perovskite solar modules. Herein, this paper reports on the recent progress of large-area perovskite solar cells. A deeper understanding of the crystallization of perovskite films is indeed essential for large-area perovskite film formation. Various large-area coating methods are proposed including blade, slot-die, evaporation, and post-treatment, where blade-coating and gas post-treatment have so far demonstrated better PCEs for an area larger than 10 cm 2 . However, PCE loss rate is estimated to be 1.4 × 10 −2 % cm −2 , which is 82 and 3.5 times higher than crystalline Si (1.7 × 10 −4 % cm −2 ) and thin film technologies (≈4 × 10 −3 % cm −2 ) respectively. Therefore, minimizing PCE loss upon scaling-up is expected to lead to PCE over 20% in case of cell efficiency of >23%.

The conventional precursor mixture based on highly pure and expensive PbI2 (purity >99.99%) is problematic in commercializing perovskite solar cells (PSCs) because of a large deviation in the batch-to-batch photovoltaic performance due to underlying nonstoichiometry and/or the nonperovskite phase. Here, we report on reproducibly efficient (>21%) PSCs based on the ambient-temperature-stable δ-phase FAPbI3 powder, synthesized by reacting PbI2 (either homemade or low-grade commercial product with purity <99%) with formamidinium iodide (FAI) at room temperature (∼93% yield). X-ray diffraction patterns confirm that annealing the spin-coated film leads to phase purity of cubic α FAPbI3. As compared to the conventional precursor mixture based on PbI2 (purity = 99.9985%), significantly reducing defects in the powder-based film is responsible for the stable and reproducible efficiency. In addition, the homogeneous light-intensity-dependent surface photocurrent contributes to the reproducibility of photovoltaic performance. The quasi-steady-state power conversion efficiency of 21.07% is certified for the device based on FAPbI3 powder.