Controlled Crystal Growth of All-Inorganic CsPbI2Br via Sequential Vacuum Deposition for Efficient Perovskite Solar Cells.

Vacuum deposition of perovskites is a promising method for scale-up fabrication and uniform film growth. However, improvements in the photovoltaic performance of perovskites are limited by the fabrication of perovskite films, which are not optimized for high device efficiency in the vacuum evaporation process. Herein, we fabricate CsPbI2Br perovskite with high crystallinity and larger grain size by controlling the deposition sequence between PbI2 and CsBr. The nucleation barrier for perovskite formation is significantly lowered by first evaporating CsBr and then PbI2 (CsBr-PbI2), followed by the sequential evaporation of multiple layers. The results show that the reduced Gibbs free energy of CsBr-PbI2, compared with that of PbI2-CsBr, accelerates perovskite formation, resulting in larger grain size and reduced defect density. Furthermore, surface-modified homojunction perovskites are fabricated to efficiently extract charge carriers and enhance the efficiency of perovskite solar cells (PeSCs) by modulating the final PbI2 thickness before thermal annealing. Using these strategies, the best PeSC exhibits a power conversion efficiency of 13.41% for a small area (0.135 cm2), the highest value among sequential thermal deposition inorganic PeSCs, and 11.10% for a large area PeSC (1 cm2). This study presents an effective way to understand the crystal growth of thermally deposited perovskites and improve their performance in optoelectronic devices.

Improved photovoltaic performance and stability of perovskite solar cells by adoption of an n-type zwitterionic cathode interlayer.

Recently, inverted perovskite solar cells (PeSCs) have witnessed significant advancements; however, their long-term stability remains a challenge because of the oxidation of silver cathodes to form AgI by mobile iodides. To overcome this problem, we propose the integration of an electron-deficient naphthalene diimide-based zwitterion (NDI-ZI) as the cathode interlayer. Compared to the physical ion-blocking layer, it effectively captures ions by forming ionic bonds via electrostatic Coulombic interaction to suppress the migration of iodide and Ag ions. The NDI-ZI interlayer also suppresses the shunt paths and modulates the work function of the Ag electrode by forming interface dipoles, thereby enhancing charge extraction. FA0.85Cs0.15PbI3 based PeSCs incorporating NDI-ZI exhibited a noticeably high power conversion efficiency of up to 23.3% and outstanding stability, maintaining ∼80% of their initial performance over 1500 h at 85 °C and over 500 h under continuous 1-sun illumination. This study highlights the potential of a zwitterionic cathode interlayer in diverse perovskite optoelectronic devices, leading to their improved efficiency and stability.

Anionic Conjugated Polyelectrolyte as a Semiconducting Additive for Efficient and Stable Perovskite Solar Cells.

Perovskite defects are a major hurdle in the efficiency and stability of perovskite solar cells (PSCs). While various defect passivation materials have been explored, most are insulators that hinder charge transport. This study investigates the potential of two different π-conjugated polyelectrolytes (CPEs), MPS2-TEA and PCPDTBT2-TMA, as semiconducting additives in PSCs. The CPEs differ in electrical conductivity, offering a unique approach to bridge defect mitigation and charge carrier transport. Unlike previous uses of CPEs mainly as interlayers or charge transport layers, we explore their direct effect on defect passivation within a perovskite layer. Secondary ion microscopy reveals the even distribution of CPEs within the perovskite layer and their efficient defect passivation potential is studied through various spectroscopic analyses. Comparing MPS2-TEA and PCPDTBT2-TMA, we find MPS2-TEA to be superior in defect passivation. The highly conductive nature of PCPDTBT2-TMA due to self-doping diminishes its defect passivation ability. The negative sulfonate groups in the side chains of PCPDTBT2-TMA stabilize polarons, reducing defect passivation capability. Finally, the PSCs with MPS2-TEA achieve remarkable power conversion efficiencies (PCEs) of 22.7% for 0.135 cm2 and 20.0% for large-area (1 cm2) cells. Furthermore, the device with MPS2-TEA maintained over 87.3% of initial PCE after 960 h at continuous 1-sun illumination and 89% of PCE after 850 h at 85 °C in a nitrogen glovebox without encapsulation. This highlights CPEs as promising defect passivation additives, unlocking potential for improved efficiency and stability not only in PSCs but also in wider applications.

Multifunctional Conjugated Molecular Additives for Highly Efficient Perovskite Light-Emitting Diodes.

Further optimization of perovskite light-emitting diodes (PeLEDs) is impeded by crystal deformation caused by residual stress and defect formation with subsequent non-radiative recombination. Molecular additives for defect passivation are widely studied; however, the majority have insulating properties that hinder charge injection and transport. Herein, highly efficient green-emitting PeLEDs are reported by introducing semiconducting molecular additives (Fl-OEGA and Fl-C8A). Transmission electron microscopy shows that conjugated additives exist primarily at the grain boundaries of perovskite, and Kelvin probe force microscopy confirms that the variation in contact potential difference between grain boundaries and perovskite crystal domains is significantly reduced. The residual tensile stress is reduced by 13% and the activation energy for ion migration increases in the Fl-OEGA-treated perovskite film, compared to those of the film without additives. Compared to insulating 2,2'-(ethylenedioxy)diethylamine (EDEA), the introduction of semiconducting additives prevents a significant reduction in the charge-transport capability. Furthermore, the PeLEDs with Fl-OEGA show a negligible shift in the turn-on voltage and a significantly smaller decrease in the current density with increasing Fl-OEGA compared to the devices with EDEA. Finally, the 3D CsPbBr3 -PeLEDs show the highest external quantum efficiency of 21.3% by the incorporation of semiconducting Fl-OEGA as a new multifunctional additive.

Triphenylamine-Based Conjugated Polyelectrolyte as a Hole Transport Layer for Efficient and Scalable Perovskite Solar Cells.

π-Conjugated polyelectrolytes (CPEs) have been studied as interlayers on top of a separate hole transport layer (HTL) to improve the wetting, interfacial defect passivation, and crystal growth of perovskites. However, very few CPE-based HTLs have been reported without rational molecular design as ideal HTLs for perovskite solar cells (PeSCs). In this study, the authors synthesize a triphenylamine-based anionic CPE (TPAFS-TMA) as an HTL for p-i-n-type PeSCs. TPAFS-TMA has appropriate frontier molecular orbital (FMO) levels similar to those of the commonly used poly(bis(4-phenyl)-2,4,6-trimethylphenylamine) (PTAA) HTL. The ionic and semiconducting TPAFS-TMA shows high compatibility, high transmittance, appropriate FMO energy levels for hole extraction and electron blocking, as well as defect passivating properties, which are confirmed using various optical and electrical analyses. Thus, the PeSC with the TPAFS-TMA HTL exhibits the best power conversion efficiency (PCE) of 20.86%, which is better than that of the PTAA-based device (PCE of 19.97%). In addition, it exhibits negligible device-to-device variations in its photovoltaic performance, contrary to the device with PTAA. Finally, a large-area PeSC (1 cm2 ) and mini-module (3 cm2 ), showing PCEs of 19.46% and 18.41%, respectively, are successfully fabricated. The newly synthesized TPAFS-TMA may suggest its great potential as an HTL for large-area PeSCs.

Preformulation and formulation of newly synthesized QNT3-18 for development of a skin whitening agent.

New molecules having the structure of (E)-2-(4-tert-butylbenzylidene) hydrazinecarbothioamide (QNT3-18) or 4-tert-butylphenylthiourea (QNT3-20) was synthesized and presupposed to inhibit melanogenesis through the inhibition of tyrosinase, which is involved in melanin formation. Therefore, we seek to develop these new molecules as skin whitening agents in topical formulations based on preformulation studies. QNT3-18 or QNT3-20 showed a strong single endothermic peak at 159.34°C with 10.79 µm-sized or at 150.69°C with 9.0 µm-sized aggregated particles, respectively. Both QNT3-18 and QNT3-20 did not show cytotoxicity at effective concentration range (0.4 µM) against keratinocyte cells and QNT3-18 was more retained than QNT3-20 in the skin instead of permeating through the skin. QNT3-18 or QNT3-20 was practically insoluble in water; the aqueous solubility was 3.8 ± 0.37 or 130.6 ± 2.52 µg/mL, respectively. Also, the partition coefficient value (log P) corresponding to the quotient between aqueous and octanol concentration of the molecule was 3.9 or 2.6, respectively. The skin retention amount of QNT3-18 was 1.7-fold higher than that of QNT3-20. When the optimal SLN cream (J3 formulation) containing 4 µM QNT3-18 was applied on the backs of hairless rats for 4 days after UV irradiation for 7 days and the skin color was checked by reflectance spectrophotometer, the rat skin treated with SLN cream with QNT3-18 quickly recovered to normal compared to skin treated with SLN cream without QNT3-18. Taken together, this study suggests that topical formulations such as creams including SLNs with QNT3-18 might be appropriate carriers for skin whitening agents.

Practical preparation procedures for docetaxel-loaded nanoparticles using polylactic acid-co-glycolic acid.

BACKGROUND: Nanoparticles fabricated from the biodegradable and biocompatible polymer, polylactic-co-glycolic acid (PLGA), are the most intensively investigated polymers for drug delivery systems. The objective of this study was to explore fully the development of a PLGA nanoparticle drug delivery system for alternative preparation of a commercial formulation. In our nanoparticle fabrication, our purpose was to compare various preparation parameters. METHODS: Docetaxel-loaded PLGA nanoparticles were prepared by a single emulsion technique and solvent evaporation. The nanoparticles were characterized by various techniques, including scanning electron microscopy for surface morphology, dynamic light scattering for size and zeta potential, x-ray photoelectron spectroscopy for surface chemistry, and high-performance liquid chromatography for in vitro drug release kinetics. To obtain a smaller particle, 0.2% polyvinyl alcohol, 0.03% D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), 2% Poloxamer 188, a five-minute sonication time, 130 W sonication power, evaporation with magnetic stirring, and centrifugation at 8000 rpm were selected. To increase encapsulation efficiency in the nanoparticles, certain factors were varied, ie, 2-5 minutes of sonication time, 70-130 W sonication power, and 5-25 mg drug loading. RESULTS: A five-minute sonication time, 130 W sonication power, and a 10 mg drug loading amount were selected. Under these conditions, the nanoparticles reached over 90% encapsulation efficiency. Release kinetics showed that 20.83%, 40.07%, and 51.5% of the docetaxel was released in 28 days from nanoparticles containing Poloxamer 188, TPGS, or polyvinyl alcohol, respectively. TPGS and Poloxamer 188 had slower release kinetics than polyvinyl alcohol. It was predicted that there was residual drug remaining on the surface from x-ray photoelectron spectroscopy. CONCLUSION: Our research shows that the choice of surfactant is important for controlled release of docetaxel.

In vitro characterization of the invasiveness of polymer microneedle against skin.

The micro-sized needles could pierce the skin to deliver drugs effectively in a minimally invasive and painless manner. However, there are only a few reports that identify the invasiveness and painlessness of microneedle (MN), and in vitro characterization studies were conducted to examine the invasiveness of MN in experimental animals and healthy volunteers. First, a fluorescent molecule was applied to show the skin holes according to the application time of MN and then the whitening effect in UV-exposed hairless rats was observed using reflectance spectroscopy according to the application time of MN. The extent of skin irritation by the application time of MN in healthy volunteers was determined from the value of skin redness. Regardless of MN application time, skin redness occurred and then disappeared 30 min after removal of MN; this phenomenon was insignificant with the application time of MN. Thus, if the MN was applied, a skin hole appeared, skin redness was observed and then the skin redness disappeared 30 min after removal of MN. Taken together, polymer MN might be a suitable tool for safe transdermal drug delivery of small molecules.

Overlap of Erosive and Non-erosive Reflux Diseases With Functional Gastrointestinal Disorders According to Rome III Criteria.

BACKGROUND/AIMS: Gastroesophageal reflux disease (GERD) is increasing in Asian countries. Functional dyspepsia (FD) or irritable bowel syndrome (IBS) are also prevalent and commonly overlapped with GERD. This study was conducted to compare the proportion and risk factors for overlapping reflux esophagitis (RE) and non-erosive reflux disease (NERD) with functional gastrointestinal disorders (FGIDs). METHODS: A total of 2,388 [male, 55.9%; mean age (+/- SD), 43.2 years (+/- 8.4)] Korean subjects who underwent the upper endoscopy for health screening were prospectively included. The subjects were asked about demographic, medical and social history by using a structured questionnaire, and FD and IBS were assessed according to the Rome III criteria. RESULTS: The subjects with RE were 286 (12.0%, male 88.5%, 42.8 years) and 74 subjects had NERD (3.1%) while the prevalence of FD and IBS were 8.1% and 10.1%, respectively. The proportion of FD and IBS in NERD was higher than that of RE (74.3% vs. 10.5%, p = 0.000; 41.9% vs. 11.2%, p = 0.000, respectively). The epigastric pain syndrome (EPS) was more prevalent than postprandial distress syndrome in NERD. According to multiple regression analysis, high somatization score and the presence of FD increased the odd ratio for NERD. However, male gender and current smoker were significant risk factors for RE. CONCLUSIONS: Compared to RE, NERD is more frequently overlapped with FD, especially EPS, and also are associated with significantly increased frequency of IBS. Our data draws attention to the possibility of subgrouping FGIDs and GERD to be important in understanding the pathophysiology of these conditions.

[Analysis of risk factors for low bone mineral density in patients with inflammatory bowel disease].

BACKGROUND/AIMS: Several clinical risk factors for low bone mineral density (BMD) in the patients with inflammatory bowel disease (IBD) have been suggested. However, its prevalence and pathophysiology in Korean population have not been fully studied. The aim of this study was to investigate the prevalence and risk factors for low BMD in Korean IBD patient. METHODS: BMD of the lumbar spine and femur was evaluated using dual-energy X-ray absorptiometry in 30 patients with IBD. Biochemical parameters of bone metabolism, such as serum calcium, phosphorus, osteocalcin, and deoxypyridinoline were measured. The associations between low BMD and clinical parameters such as disease duration, disease activity, drug history, body mass index (BMI), and others were evaluated retrospectively using medical records. RESULTS: Low BMD at the lumbar spine or femur was observed in 63.3% of the patients, and there was no significant difference between the patients with Crohns disease and ulcerative colitis. Clinical and biochemical parameters were irrelevant to BMD. In the patients without glucocorticoid treatment prior to BMD measurement, already 50.0% of patients had low BMD. CONCLUSIONS: Low BMD is a common feature in Korean IBD patients, even those who do not use glucocorticoid. The multiple factors may be involved in the pathogenesis of low BMD. Therefore, BMD should be examined in all IBD patients, irrespective of glucocorticoid treatment.

Effect of applying modes of the polymer microneedle-roller on the permeation of L-ascorbic acid in rats.

Despite the advantages of drug delivery through skin, transdermal drug delivery is only used with a small subset of drugs because most compounds cannot cross the skin at therapeutically useful rates. Recently, a new concept known as microneedle was introduced and could be used to pierce effectively to deliver drugs using micron-sized needles in a minimally invasive and painless manner. In this study, the polymer microneedle-roller was fabricated so that it can be applied into the permeation of L-ascorbic acid. Moreover, a recent publication suggested the possibility of ascorbic acid 2-phosphate as a hair restorer; hence, this study was carried out to check the effect of L-ascorbic acid itself on the hair growing rate in rats according to the presence of various application frequencies of the polymer microneedle-roller. When the polymer microneedle-roller was applied nine times with four directions into rat's shaved skin, the permeation of L-ascorbic acid increased by 10.54-fold compared to that of the absence of the polymer microneedle-roller. The histological examination revealed that the skin pretreated with various application frequencies of the polymer microneedle-roller had more transport pathways. The faster hair growing phenomenon was observed in the presence of polymer microneedle-roller compared to the absence of the polymer microneedle-roller.

T lymphocytes and dendritic cells are activated by the deletion of peroxiredoxin II (Prx II) gene.

Peroxiredoxin II (Prx II) is a member of antioxidant enzyme family and it plays a protective role against oxidative damage. Constitutive production of endogenous reactive oxygen species was detected in spleen and bone marrow cells lacking Prx II. Here, we investigated the role of Prx II in immune responses. The total number of splenocytes (especially, the population of S-phase cells and CD3(+) T cells) was significantly higher in Prx II(-/-) mice than in wild type. Number of peripheral blood mononuclear cells (PBMCs) in Prx II(-/-) mice was also higher than wild type. Differentiation of Prx II(-/-) mouse bone marrow cells into CD11c-positive dendritic cells was greater than that of wild type. Transplantation of Prx II(-/-) bone marrow cells into wild type mice increased PBMCs in blood and bone marrow-derived dendritic cells. Prx II deletion enhances concanavalin A (ConA)-induced splenocyte proliferation and mixed lymphocyte reaction (MLR) activity of bone marrow-derived CD11c-positive dendritic cells to stimulate recipient splenocytes. Collectively, these data suggest that Prx II inhibits the immune cell responsiveness, which may be regulated by scavenging the low amount of reactive oxygen species (ROS).