Twisted Carotenoids Do Not Support Efficient Intramolecular Singlet Fission in the Orange Carotenoid Protein.

Singlet exciton fission is the spin-allowed generation of two triplet electronic excited states from a singlet state. Intramolecular singlet fission has been suggested to occur on individual carotenoid molecules within protein complexes provided that the conjugated backbone is twisted out of plane. However, this hypothesis has been forwarded only in protein complexes containing multiple carotenoids and bacteriochlorophylls in close contact.

Iron Deficiency among School-Aged Adolescents in Hong Kong: Prevalence, Predictors, and Effects on Health-Related Quality of Life.

Iron deficiency (ID) is a prevalent nutritional deficiency affecting children/adolescents worldwide. We reported (1) the prevalence of ID and ID with anemia (IDA) among Chinese school-aged adolescents, (2) clinical and dietary predictors of iron status, and (3) its impact on health-related qualities of life (HRQoL). This cross-sectional study recruited 183 boys and 340 girls (mean age = 17.

Highly efficient p-i-n perovskite solar cells that endure temperature variations.

Daily temperature variations induce phase transitions and lattice strains in halide perovskites, challenging their stability in solar cells. We stabilized the perovskite black phase and improved solar cell performance using the ordered dipolar structure of β-poly(1,1-difluoroethylene) to control perovskite film crystallization and energy alignment. We demonstrated p-i-n perovskite solar cells with a record power conversion efficiency of 24.

Toward Improved Environmental Stability of Polymer:Fullerene and Polymer:Nonfullerene Organic Solar Cells: A Common Energetic Origin of Light- and Oxygen-Induced Degradation.

With the emergence of nonfullerene electron acceptors resulting in further breakthroughs in the performance of organic solar cells, there is now an urgent need to understand their degradation mechanisms in order to improve their intrinsic stability through better material design. In this study, we present quantitative evidence for a common root cause of light-induced degradation of polymer:nonfullerene and polymer:fullerene organic solar cells in air, namely, a fast photo-oxidation process of the photoactive materials mediated by the formation of superoxide radical ions, whose yield is found to be strongly controlled by the lowest unoccupied molecular orbital (LUMO) levels of the electron acceptors used. Our results elucidate the general relevance of this degradation mechanism to both polymer:fullerene and polymer:nonfullerene blends and highlight the necessity of designing electron acceptor materials with sufficient electron affinities to overcome this challenge, thereby paving the way toward achieving long-term solar cell stability with minimal device encapsulation.

Tail state limited photocurrent collection of thick photoactive layers in organic solar cells.

We analyse organic solar cells with four different photoactive blends exhibiting differing dependencies of short-circuit current upon photoactive layer thickness. These blends and devices are analysed by transient optoelectronic techniques of carrier kinetics and densities, air photoemission spectroscopy of material energetics, Kelvin probe measurements of work function, Mott-Schottky analyses of apparent doping density and by device modelling. We conclude that, for the device series studied, the photocurrent loss with thick active layers is primarily associated with the accumulation of photo-generated charge carriers in intra-bandgap tail states.

Hepatitis E virus infection in Hong Kong blood donors.

Background And Objectives: In Hong Kong, the dominant circulating hepatitis E virus (HEV) genotype is type 4, which can cause more severe clinical consequences than type 3. The aim of this study was to determine the HEV prevalence in Hong Kong blood donors.

Materials And Methods: Unlinked donation samples (n = 10 000) collected in March to May 2015 were tested for HEV RNA using the Procleix HEV assay in an individual donation format (IDT).

A combined transient photovoltage and impedance spectroscopy approach for a comprehensive study of interlayer degradation in non-fullerene acceptor organic solar cells.

Organic solar cells utilise thin interlayer materials between the active layer and metal electrodes to improve stability and performance. In this work, we combine transient photovoltage (TPV) and impedance spectroscopy (EIS) measurements to study how degradation affects both the active layer and the interlayer. We show that neither technique alone can provide a complete insight into both of these regions: TPV is more suited to studying degradation of the active layer; EIS clearly identifies the properties of the interlayer.

Curriculum design and attrition among undergraduate nursing students: A systematic review.

Attrition rates among nursing students are a global issue, and a possible factor in current nursing shortages. Numerous studies have been conducted to determine why students drop out of nursing programmes. The limitations of previous studies have included overly small sample sizes, being largely descriptive, and not focusing on attrition as an outcome.

Photo-stability study of a solution-processed small molecule solar cell system: correlation between molecular conformation and degradation.

Solution-processed organic small molecule solar cells (SMSCs) have achieved efficiency over 11%. However, very few studies have focused on their stability under illumination and the origin of the degradation during the so-called burn-in period. Here, we studied the burn-in period of a solution-processed SMSC using benzodithiophene terthiophene rhodamine:[6,6]-phenyl C butyric acid methyl ester (BTR:PCBM) with increasing solvent vapour annealing time applied to the active layer, controlling the crystallisation of the BTR phase.

One-step growth of thin film SnS with large grains using MOCVD.

Thin film tin sulphide (SnS) films were produced with grain sizes greater than 1 μm using a one-step metal organic chemical vapour deposition process. Tin-doped indium oxide (ITO) was used as the substrate, having a similar work function to molybdenum typically used as the back contact, but with potential use of its transparency for bifacial illumination. Tetraethyltin and ditertiarybutylsulphide were used as precursors with process temperatures 430-470 °C to promote film growth with large grains.

Impact of Aggregation on the Photochemistry of Fullerene Films: Correlating Stability to Triplet Exciton Kinetics.

The photochemistry and stability of fullerene films is found to be strongly dependent upon film nanomorphology. In particular, PCBM blend films, dispersed with polystyrene, are found to be more susceptible to photobleaching in air than the more aggregated neat films. This enhanced photobleaching correlated with increased oxygen quenching of PCBM triplet states and the appearance of a carbonyl FTIR absorption band indicative of fullerene oxidation, suggesting PCBM photo-oxidation is primarily due to triplet-mediated singlet oxygen generation.