Nongeminate Recombination in All-Polymer Solar Cells with Different Crystallinities.

One of the most challenging issues facing the organic photovoltaic community is to realize a high fill factor (FF) even with thick active layers. This is because the thick active layer is beneficial for photon absorption but makes charge collection difficult, which is primarily restricted by nongeminate recombination in solar cells. In this work, we have studied nongeminate recombination in four kinds of polymer solar cells based on blends of donor-conjugated polymers with different crystallinities and acceptor-conjugated polymers with a naphthalene diimide unit by using transient photovoltage and photocurrent techniques. As a result, we find that nongeminate recombination is considerably suppressed with an increasing degree of crystallinity of donor polymers, leading to a high FF of more than 0.6 even with an active layer thickness of 300 nm. The origin of such a phenomenon is further discussed in terms of variations in the states of mixed phases with a cascaded energy structure between crystalline domains and amorphous domains evaluated by conductive atomic force microscopy.

Life-History Traits of a Subtropical Cerambycid Beetle, Ropica honesta (Coleoptera: Cerambycidae).

Ropica honesta Pascoe is a small-sized cerambycid that has been recorded in tropical to subtropical Asia. In this study, life-history traits were examined for a local population collected from Iriomote Island (24.3°N, 123.8°E), Okinawa, Japan, by rearing insects on artificial diet as larval food. The egg period was 5.9 ± 0.3 d at 25°C. There was no significant difference in the duration of the larval, pupal, and adult preoviposition periods between long-day (14:10 [L:D]) and short-day (12:12 [L:D]) photoperiods at both 20 and 25°C. These periods at 25°C (14:10 [L:D]) were 28.5 ± 1.4, 8.4 ± 0.5, and 9.6 ± 1.9 d (mean ± SD), respectively. The relationship between the developmental rate and temperature followed the law of total effective temperature; thus, the developmental threshold temperature and thermal constant were estimated based on these data. Together with the finding that R. honesta may not have diapause in the egg stage, it is suggested that this beetle does not have diapause in the life cycle. Furthermore, when larvae were reared on natural food (dead twigs of hardwoods) adults emerged from the twigs 47.6 ± 2.9 d after oviposition, and this value was close to the total duration of the egg to pupal periods. Together with the data for annual temperature of the habitat and the fact that food resources for the species (dead twigs and leaves of hardwoods) are available throughout the year, we conclude that R. honesta develops and reproduces all year round, with five generations at maximum.

Block copolymer-mediated synthesis of gold nanoparticles in aqueous solutions: segment effect on gold ion reduction, stabilization, and particle morphology.

We report here on the segment effects of poly(ethylene oxide)-containing block copolymers (PEO-BCP) on the reduction activity for tetrachloride gold(III) ([AuCl(4)](-)), interfacial activity for gold surface, colloidal stability, and morphology of gold nanoparticles formed in aqueous solutions. In particular, the effects of poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), polyethylene (PE) segments and amino group (NH(2)) on the rate of [AuCl(4)](-) reduction, adsorption of PEO-BCP onto gold surface, colloidal stability, and morphology of gold nanoparticles formed in aqueous solutions were examined using a poly(ethylene oxide)-poly(propylene oxide) triblock copolymer (PEO-PPO-PEO, Pluronic L44), an amino-terminated poly(ethylene oxide)-poly(propylene oxide) block copolymer (PEO-PPO-NH(2), SURFONAMINE® L-207), a poly(ethylene oxide) homopolymer (PEO, poly(ethylene glycol)2000), and a polyethylene-poly(ethylene oxide) block copolymer (PE-PEO). We found that the reduction activity of PEO-BCP for [AuCl(4)](-) became higher with the order of PEO-PPO-NH(2)

High-power direct green laser oscillation of 598 mW in Pr(3+)-doped waterproof fluoroaluminate glass fiber excited by two-polarization-combined GaN laser diodes.

We demonstrated a high-power and highly efficient Pr-doped waterproof fluoride glass fiber laser at 522.2 nm excited by two-polarization-combined GaN laser diodes and achieved a subwatt output power of 598 mW and slope efficiency of 43.0%. This system will enable us to make a vivid laser display, a photocoagulation laser for eye surgery, a color confocal scanning laser microscope, and an effective laser for material processing. Direct visible ultrashort pulse generation is also expected.