Heteroepitaxial growth of ZnO branches selectively on TiO2 nanorod tips with improved light harvesting performance

A seeded heteroepitaxial growth of ZnO nanorods selectively on TiO2 nanorod tips was achieved by restricting crystal growth on highly hydrophobic TiO2 nanorod film surfaces. Intriguing light harvesting performance and efficient charge transport efficiency has been found, which suggest potential applications in photovoltaics and optoelectronics

Every coin has two sides : the challenge of addressing inappropriate prescribing in older patients in primary care

Background: Drug-related morbidity contributes to every tenth unplanned hospital admission in older patients. A way to address this problem is to identify and minimize potentially inappropriate prescribing (PIP). Two important types of PIP are the use of contraindicated or excessively dosed drugs in patients with renal impairment and drug-disease interactions, where a drug worsens a concomitant disease. It is largely unknown how commonly older patients (≥ 65) are exposed to these two types of PIP. Similarly, there is insufficient knowledge on how general practitioners (GPs) and nurses in primary care should address PIP in their older patients. One important step in understanding how to address PIP is to investigate GPs’ and nurses’ views on PIP and medication reviews. Aim: 1) To increase knowledge on how commonly older patients in primary care are exposed to PIP in relation to renal function and drug-disease interactions; 2) To examine if an intervention on medication reviews combining several evidencebased educational strategies is a valuable measure to address PIP in primary care; and 3) To understand GPs’ and nurses’ views on PIP and medication reviews. Material and methods: Two cross-sectional population-based studies (I+II) in patients aged ≥65 in primary care in Stockholm County were performed. Drug dispense was assessed during one year. PIP in relation to renal function was assessed in patients with chronic kidney disease stage 3 (n=30 372) or 4 (n=2161) according to CKD-EPI formula (I). Drug-disease interactions were analyzed among 336 295 patients. PIP was addressed in a cluster-randomized controlled trial including 69 primary care practices (III). The multifaceted educational intervention targeted GPs and nurses, with the aim to promote medication reviews in accordance with a new regulation, thus reduce PIP and unplanned healthcare use. Data (I-III) were derived from regional and national registers (diagnoses, drugs, healthcare use) and SCREAM database (creatinine). Qualitative data were collected after each educational session and explored with thematic analysis (IV). Results: I: Contraindicated medicines were used by 9% of patients with chronic kidney disease stage 3 compared to 38% with stage 4, and excessive dosing was present in 43% vs. 58%, respectively. II: Drug-disease interactions were found in 10.8 % of older adults, the most common was hypertension/NSAID. I+II: A limited number of potentially inappropriate medicines explained the majority of PIP, such as NSAIDs (I + II) and drugs acting on the renin-angiotensin-aldosterone system (I). III: Neither PIP nor unplanned healthcare decreased after a multifaceted educational intervention in primary care. IV: A possible explanation for this result is the complexity of prescribing in older patients, as expressed by GPs and nurses. Conclusions: In patients with impaired renal function, excessive dosing was more common than the use of contraindicated medicines. Drug-disease interactions were less common than PIP in relation to renal function. Both types of PIP seem manageable as only a few medicines are implicated. Medication reviews that address PIP in its entirety are difficult to implement in primary care and may not improve prescribing in older patients. According to GPs and nurses, the complexity of PIP is a major challenge. Their efforts to improve prescribing are undermined by this complexity. In view of the potential harm of PIP in older patients, it is crucial to continue research on how it may be decreased

Entwicklung eines optoelektronischen Sehhilfesystems

In dieser Arbeit wird ein mobiles optoelektronisches Sehhilfesystem fuer stark sehbehinderte Personen vorgestellt. Es hat das Ziel, die durch ihre Behinderung eingeschraenkte Mobilitaet dieser Personengruppe zu verbessern. Dazu wird die Umgebung mit einem spezeill fuer solche Aufgaben entwickelten Kamera-Chip aufgenommen und mit Hilfe einer elektronischen Brille Ausgegeben. Diese besteht aus zwei LCDs fuer die Bildausgabe und einer Optik, die das Bild vergroessert auf die Netzhaut des Patienten abbildet. Die auszugebende Bilddaten koennen mit Hilde eines Noetbooks bearbeitet werden. Das Neuartige an diesem System ist, dass es Sehbehinderten ermoeglicht, neben Einstellungen von Kontrast, Helligkeit und Vergroesserung des Originalbildes auch eine Bildverarbeitung wie z.B. Kantenverstaerkung zu waehlen

Quantification of Ion Migration in CH3NH3PbI3 Perovskite Solar Cells by Transient Capacitance Measurements

Solar cells based on organic-inorganic metal halide perovskites show efficiencies close to highly-optimized silicon solar cells. However, ion migration in the perovskite films leads to device degradation and impedes large scale commercial applications. We use transient ion-drift measurements to quantify activation energy, diffusion coefficient, and concentration of mobile ions in methylammonium lead triiodide (MAPbI3) perovskite solar cells, and find that their properties change close to the tetragonal-to-orthorhombic phase transition temperature. We identify three migrating ion species which we attribute to the migration of iodide (I-) and methylammonium (MA+). We find that the concentration of mobile MA+ ions is one order of magnitude higher than the one of mobile I- ions, and that the diffusion coefficient of mobile MA+ ions is three orders of magnitude lower than the one for mobile I- ions. We furthermore observe that the activation energy of mobile I- ions (0.29 eV) is highly reproducible for different devices, while the activation energy of mobile MA+ depends strongly on device fabrication. This quantification of mobile ions in MAPbI3 will lead to a better understanding of ion migration and its role in operation and degradation of perovskite solar cells

Research Update: Behind the high efficiency of hybrid perovskite solar cells

Perovskite solar cells (PSCs) marked tremendous progress in a short period of time and offer bright hopes for cheap solar electricity. Despite high power conversion efficiency >20%, its poor operational stability as well as involvement of toxic, volatile, and less-abundant materials hinders its practical deployment. The fact that degradation and toxicity are typically observed in the most successful perovskite involving organic cation and toxic lead, i.e., CH3NH3PbX3, requires a deep understanding of their role in photovoltaic performance in order to envisage if a non-toxic, stable yet highly efficient device is feasible. Towards this, we first provide an overview of the basic chemistry and physics of halide perovskites and its correlation with its extraordinary properties such as crystal structure, bandgap, ferroelectricity, and electronic transport. We then discuss device related aspects such as the various device designs in PSCs and role of interfaces in origin of PV parameters particularly open circuit voltage, various film processing methods and their effect on morphology and characteristics of perovskite films, and the origin and elimination of hysteresis and operational stability in these devices. We then identify future perspectives for stable and efficient PSCs for practical deployment

Highly Efficient Reproducible Perovskite Solar Cells Prepared by Low-Temperature Processing

In this work, we describe the role of the different layers in perovskite solar cells to achieve reproducible, similar to 16% efficient perovskite solar cells. We used a planar device architecture with PEDOT:PSS on the bottom, followed by the perovskite layer and an evaporated C-60 layer before deposition of the top electrode. No high temperature annealing step is needed, which also allows processing on flexible plastic substrates. Only the optimization of all of these layers leads to highly efficient and reproducible results. In this work, we describe the effects of different processing conditions, especially the influence of the C-60 top layer on the device performance

Humidity Versus Photo-Stability of Metal Halide Perovskite Films in a Polymer Matrix

Despite the high efficiency of over 21% reported for emerging thin film perovskite solar cells, one of the key issues prior to their commercial deployment is to attain their long term stability under ambient and outdoor conditions. The instability in perovskite is widely conceived to be humidity induced due to the water solubility of its initial precursors, which leads to decomposition of the perovskite crystal structure; however, we note that humidity alone is not the major degradation factor and it is rather the photon dose in combination with humidity exposure that triggers the instability. In our experiment, which is designed to decouple the effect of humidity and light on perovskite degradation, we investigate the shelf-lifetime of CH3NH3PbI3 films in the dark and under illumination under high humidity conditions (Rel. H. > 70%). We note minor degradation in perovskite films stored in a humid dark environment whereas upon exposure to light, the films undergo drastic degradation, primarily owing to the reactive TiO2/perovskite interface and also the surface defects of TiO2. To enhance its air-stability, we incorporate CH3NH3PbI3 perovskite in a polymer (poly-vinylpyrrolidone, PVP) matrix which retained its optical and structural characteristics in the dark for ∼2000 h and ∼800 h in room light soaking, significantly higher than a pristine perovskite film, which degraded completely in 600 h in the dark and in less than 100 h when exposed to light. We attribute the superior stability of PVP incorporated perovskite films to the improved structural stability of CH3NH3PbI3 and also to the improved TiO2/perovskite interface upon incorporating a polymer matrix. Charge injection from the polymer embedded perovskite films has also been confirmed by fabricating solar cells using them, thereby providing a promising future research pathway for stable and efficient perovskite solar cells

Synthesis, spectroscopic characterization and thermogravimetric analysis of two series of substituted (metallo)tetraphenylporphyrins

Subsequent treatment of H2TPP(CO2H)4 (tetra(p-carboxylic acid phenyl)porphyrin, 1) with an excess of oxalyl chloride and HNR2 afforded H2TPP(C(O)NR2)4 (R = Me, 2; iPr, 3) with yields exceeding 80%. The porphyrins 2 and 3 could be converted to the corresponding metalloporphyrins MTPP(C(O)NR2)4 (R = Me/iPr for M = Zn (2a, 3a); Cu (2b, 3b); Ni (2c, 3c); Co (2d, 3d)) by the addition of 3 equiv of anhydrous MCl2 (M = Zn, Cu, Ni, Co) to dimethylformamide solutions of 2 and 3 at elevated temperatures. Metalloporphyrins 2a–d and 3a–d were obtained in yields exceeding 60% and have been, as well as 2 and 3, characterized by elemental analysis, electrospray ionization mass spectrometry (ESIMS) and IR and UV–vis spectroscopy. Porphyrins 2, 2a–d and 3, 3a–d are not suitable for organic molecular beam deposition (OMBD), which is attributed to their comparatively low thermal stability as determined by thermogravimetric analysis (TG) of selected representatives

Probing Columnar Discotic Liquid Crystals by EPR Spectroscopy with a Rigid-Core Nitroxide Spin Probe

Discotics studied by EPR: The application of EPR spectroscopy to columnar discotic liquid crystals using a novel rigid-core nitroxide spin probe (see picture) is possible. EPR spectra measured at different temperatures across three phases of hexakis(n-hexyloxy)triphenylene show a strong sensitivity to the phase composition, molecular rotational dynamics, and columnar order