Energetic Effects of Hole Transporting Materials on the Performance of Organometal Halide Perovskite Photovoltaic Cells

Efficient, inexpensive, lightweight and flexible solar cells are desired to help meet the world’s growing energy needs. Organometal halide perovskite (OMHP) photovoltaic (PV) cells have shown dramatic increases in solar cell efficiencies increase over the last 5 years. OMHP PV cells have attracted significant attention due to their broad absorption spectra, high electron and hole mobility, and low production cost. The interface between hole transporting layer (HTL) and perovskite thin films have a significant influence on charge transfer and overall solar cell performance. 2,2’,7,7’-tetrakis(N,N-di-p-methoxyphenylamine)9,9’-spirobifluorene (Spiro-OMeTAD) is a small molecule largely used as HTL in perovskite solar cells. However, this material suffers from low charge-carrier mobilities and inappropriate energy level alignments with some perovskites. In this work we investigate the effect of the HTL energetics on the performance of perovskite solar cells. This is accomplished through employing a range of HTLs with varying ionization energies (IEs). We find that the solar cell device performance is relatively insensitive to the IE of the HTL within a 0.4 eV range. We also demonstrate that modification of the HTL surface with different alcohols helps in increasing the solar cell performances

EFFECTS OF HOLE TRANSPORTING LAYERS AND SURFACE LIGANDS ON INTERFACE ENERGETICS AND PHOTOVOLTAIC PERFORMANCE OF METHYLAMMONIUM LEAD IODIDE PEROVSKITES

Organic metal halide perovskites are promising materials for various optoelectronic device applications such as light emitting diodes (LED) and photovoltaic (PV) cells. Perovskite solar cells (PSCs) have shown dramatic increases in power conversion efficiency over the previous ten years, far exceeding the rate of improvement of all other PV technologies. PSCs have attracted significant attention due to their strong absorbance throughout the visible region, high charge carrier mobilities, color tunability, and ability to make ultralight weight devices. However, organic metal halide perovskites still face several challenges. For example, their environmental stability issue must be overcome to enable widespread commercialization. Meeting this challenge involves material and interface development and optimization throughout the whole PV device stack. Fundamental understanding of the optical properties, electrical properties, interfacial energetics, and device physics is key to overcome current challenges with PSCs. In this dissertation, we report a new family of triarylaminoethynyl silane molecules as hole transport layers (HTLs), which are in part used to investigate how the PV performance depends on the ionization energy (IE) of the HTL and provide a new and versatile HTL material platform. We find that triarylaminoethynyl silane HTLs show comparable PV performance to the state-of-the art HTLs and demonstrate that different processing conditions can influence the IE of methylammonium lead iodide (MAPbI3). Surface ligand treatment provides a promising approach to passivate defect states and improve the photoluminescence quantum yield (PLQY), charge-carrier mobilities, material and device stability, and performance of PSCs. Numerous surface treatments have been applied to perovskite films and shown to passivate defect states and improve the PLQY and performance of PSCs, but it is not clear which surface ligands bind to the surface and to what extent. As surface ligands have the potential to passivate defect states, alter interface energetics, and manipulate material and device stability, it is important to understand how different functional groups interact with the surfaces of perovskite films. We investigate a series of ligand binding groups and systematically probe the stability of the bound surface ligands, how they influence energetics, PLQYs, film stability, and PV device performance. We further explore ligand penetration and whether surface ligands prefer to remain on the surface or penetrate into the perovskite. Three variations of tail groups including aryl groups with varying extents of fluorination, bulky groups of varying size, and linear alkyl groups of varying length are examined to probe ligand penetration and the impact on material stability

Effect of natural antioxidants on the aggregation and disaggregation of beta-amyloid

Purpose: To examine the relationship between higher antioxidant activity and aggregation or disaggregation of beta-amyloid (Aβ) for 21 plants.Methods: Twenty-nine natural plant extracts and their antioxidant activities were analyzed using DPPH assay. The aggregation and disaggregation of Aβ were analyzed using Thioflavin-T assay.Results: Eleven plant extracts exhibited high antioxidant activities with the half-maximal inhibitory concentration (IC50) values < 20.0 μg/mL. Furthermore, the plant extracts efficiently inhibited Aβ aggregation with a mean IC50 value of 17.0 μg/mL. However, four plant extracts exhibiting low antioxidant activities (IC50 > 80.0 μg/mL) inhibited Aβ aggregation less efficiently with a mean IC50 value of 75.7 μg/mL. Furthermore, plant extracts with high antioxidant activities were not invariably efficient for disaggregating pre-formed Aβ aggregates.Conclusion: High antioxidant activities were positively correlated with the inhibition of Aβ aggregation, although not with the disaggregation of pre-formed Aβ aggregates. Nevertheless, potent antioxidants may be helpful in treating Alzheimer’s disease.Keywords: Alzheimer’s disease, β-Amyloid, Aggregation, Disaggregation, Antioxidant

A multidimensional approach to wearability assessment of an electronic wrist bracelet for the criminal justice system

Electronic monitoring systems have been globally adopted to track criminals to ensure public safety efficiently. In this study, we aimed to assess the wearability of an electronic bracelet using multiple evaluation methods, including the evaluation of range of motion (ROM), air gap (AG), and clothing pressure (CP) at the wearer’s wrist, as well as self-scoring of subjective comfort (SC). We recruited eight Korean male participants (N = 8) who were in their 30 s and did not have any musculoskeletal problems at data collection. We compared the test results collected on the first day with those obtained after wearing the electronic wrist bracelet for 5 consecutive days. We also examined the differences between the normal-weight and overweight groups. Overall, the data evinced a decrease in the wrist ROM, AG, and SC, but an increase in the CP after it was worn for 5 days. And, the results were more observable in the overweight group, as compared to the normal-weight group. Furthermore, this study proposed a novel and effective assessment tool that could be used to measure the wearability of devices or systems intended to be worn on the human body—not only the electronic wrist bracelet for criminal monitoring but also popular commercial electronic bracelets for sportswear or health-related monitoring system.This work was supported by Korea Institute for Advancement of Technology (KIAT) grant funded by the Korea Government (MOTIE) (P0012770, Professional Human Resources Training Project), and the National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT) (2016R1A5A1938472

Comparative analysis of FBS containing media and serum free chemically defined media, CellCor for adipose derived stem cells production

Background: As a result of the aging society, the average OECD life expectancy has grown to about 80 years, yet the average health life still remains at only 65 years, leaving more than 15 years of life in an uncertain health state. Regenerative medicine is a new concept of medicine that combines cells and biomaterials to restore the functions of aged or damaged tissues or organs. It is also a good treatment for chronic diseases and incurable diseases, receiving attention as a new paradigm for treating diseases. Problems: As the market for regenerative medicine grows, mass production of consistent quality cells is required. Media is the most important thing in mass production of consistent quality cells. However, the fetal bovine serum (FBS) containing media that is currently wide used has many problems, such as unidentified viral infection, immunogenicity, lot variations, unstable supply, and ethical issues. To solve these problems and make rapid progress in regenerative medicine, a high-performance serum free chemically defined media (CDM) is needed. Solution: CellCor is a serum free CDM that provides excellent performance, safety, economy and consistency in stem cell production. CellCor allows higher-speed cell production rate than current FBS containing culture media (Figure 1). Compared to the FBS containing media, CellCor is able to maintain stem cell markers, higher population homogeneity, genetic stability, and excellent differentiation potency even at later passage. Please click Additional Files below to see the full abstract

Charge-spin correlation in van der Waals antiferromagenet NiPS3

Strong charge-spin coupling is found in a layered transition-metal trichalcogenide NiPS3, a van derWaals antiferromagnet, from our study of the electronic structure using several experimental and theoretical tools: spectroscopic ellipsometry, x-ray absorption and photoemission spectroscopy, and density-functional calculations. NiPS3 displays an anomalous shift in the optical spectral weight at the magnetic ordering temperature, reflecting a strong coupling between the electronic and magnetic structures. X-ray absorption, photoemission and optical spectra support a self-doped ground state in NiPS3. Our work demonstrates that layered transition-metal trichalcogenide magnets are a useful candidate for the study of correlated-electron physics in two-dimensional magnetic material.Comment: 6 pages, 3 figur

Assessment of the modulation degrees of intensity-modulated radiation therapy plans

Background To evaluate the modulation indices (MIs) for predicting the plan delivery accuracies of intensity-modulated radiation therapy (IMRT) plans. Methods A total of 100 dynamic IMRT plans that used TrueBeam STx and 102 dynamic IMRT plans that used Trilogy were selected. For each plan, various MIs were calculated, which included the modulation complexity score (MCS), plan-averaged beam area (PA), plan-averaged beam irregularity (PI), plan-averaged beam modulation (PM), MI quantifying multi-leaf collimator (MLC) speeds (MIs), MI quantifying MLC acceleration (MIa), and MI quantifying MLC acceleration and segment aperture irregularity (MIc,IMRT). To determine plan delivery accuracy, global gamma passing rates, MLC errors of log files, and dose-volumetric parameter differences between original and log file-reconstructed IMRT plans were obtained. To assess the ability of each MI for predicting plan delivery accuracy, Spearmans rank correlation coefficients (rs) between MIs and plan delivery accuracy measures were calculated. Results PI showed moderately strong correlations with gamma passing rates in MapCHECK2 measurements of both TrueBeam STx and Trilogy (rs = − 0.591 with p <  0.001 and − 0.427 with p <  0.001 to with gamma criterion of 2%/2 mm, respectively). For ArcCHECK measurements, PI also showed moderately strong correlations with the gamma passing rates in the ArcCHECK measurements of TrueBeam STx and Trilogy (rs = − 0.545 with p <  0.001 and rs = − 0.581 with p <  0.001 with gamma criterion of 2%/2 mm, respectively). The PI showed the second strongest correlation with MLC errors in both TrueBeam STx and Trilogy (rs = 0.861 with p <  0.001 and rs = 0.767 with p <  0.001, respectively). In general, the PI showed moderately strong correlations with every plan delivery accuracy measure. Conclusions The PI showed moderately strong correlations with every plan delivery accuracy measure and therefore is a useful predictor of IMRT delivery accuracy.This work was supported by a National Research Foundation of Korea (NRF) grant from the Korea government (MSIP). (No.2017M2A2A7A02020639, No.2017M2A2A7A02020640, No.2017M2A2A7A02020641, No.2017M2A2A7A02020643)

A Case of Severe Anemia by Necator americanus Infection in Korea

This report describes clinical and parasitological findings of an 82-yr-old female patient who lived in a local rural village and suffered from severe chronic anemia for several years. She was transferred to the National Police Hospital in Seoul for management of severe dyspnea and dizziness. At admission, she showed symptoms or signs of severe anemia. Gastroduodenoscopy observed hyperemic mucosa of the duodenum and discovered numerous moving roundworms on the mucosa. Endoscopy isolated seven of them, which were identified as Necator americanus by characteristic morphology of cutting plates in the buccal cavity. The patient was treated with albendazole and supportive measures for anemia, and her physical condition much improved. This case suggests the possibility that hookworm N. americanus is still transmitted in a remote local mountainous area in Korea