Yoshihiro Oka

The impact of NiOx layers on the performance of inverted perovskite solar cells (PSCs) has been investigated using multiple analysis methods (thermal gravimetric, differential thermal analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and Soft X-ray photoelectron spectroscopy) of NiOx layers, which were made by spray pyrolysis deposition at different temperatures. The analyses of this study indicate that the efficiency of inverted PSC increases with the Scherrer crystallite size of NiOx. We also observed that the band state of the NiOx layer was changed by Na+ ions migrated from the glass substrate, which also had an impact on the efficiency. The results clearly showed that under high fabrication temperature, migration of matter from the substrate to the hole transport layer affects the electronic structure. Therefore, how these materials are engineered will be important to increase the efficiency of inverted PSCs.

Single-wall carbon nanotubes (SWCNTs) are promising materials for electronic applications, such as transparent electrodes and thin-film transistors. However, the dispersion of isolated SWCNTs into solvents remains an important issue for their practical applications. SWCNTs are commonly dispersed in solvents via ultrasonication. However, ultrasonication damages SWCNTs, forming defects and cutting them into short pieces, which significantly degrade their electrical and mechanical properties. Herein, we demonstrate a novel approach toward the large-scale dispersion of long and isolated SWCNTs by using hydrodynamic cavitation. Considering the results of atomic force microscopy and dynamic light-scattering measurements, the average length of the SWCNTs dispersed via the hydrodynamic cavitation method is larger than that of the SWCNTs dispersed by using an ultrasonic homogenizer.

This work studied the effects of tackifiers on the impact energy absorption properties of block copolymers (BCPs) comprising poly(styrene)-b-poly(isoprene)-b-poly(styrene) (SIS) and poly(methyl methacrylate)-b-poly(n-butyl acrylate)-b-poly(methyl methacrylate) (MAM). A rosin ester resin (RE) and an aliphatic petroleum resin (C5PR) were compared as the tackifiers. Analyses of Hansen solubility parameters and observations using electron microscopy indicated that both tackifiers were highly compatible with the poly(isoprene) component of the SIS, while the RE also showed good compatibility with the poly(n-butyl acrylate) phase of the MAM. The impact energy absorption characteristics of laminates made by applying layers of BCP/tackifier blends to cured epoxy substrates were evaluated using a pendulum impactor. The extent of energy absorption by these laminates was found to increase within specific tackifier concentration ranges. However, the C5PR showed poor compatibility with the MAM and had almost no effect on the energy absorption of the laminates. The energy absorption of the laminates could be described based on the calculated loss factor, eta, determined using the RUK equation including the viscoelastic parameters (both tan delta and storage modulus) for the BCP/tackifier blends, considering the time-temperature superposition principle, and for the laminate structures.

Pt nanoparticles were synthesized by a cavitation bubble plasma (CBP) with a pair of Pt rod electrodes. Pt nanoparticles were loaded on TiO2 particles to produce Pt/TiO2 photocatalysts. Regardless of the processing time during nanoparticle synthesis, the Pt nanoparticles were spherical shape of diameter about 1.5 to 3.0 nm. Pt nanoparticles supported on TiO2 particles increased in particle size due to agglomeration with increasing processing time. The hydrogen production amount by the photocatalytic reaction of Pt/TiO2 in glycerol solution increased with increasing CBP processing time, reaching 71.1 μmol/h at 5 minutes of processing time.

The effect of solution temperature on the generation of cavitation bubble plasma was investigated for the purpose of improving the plasma generation rate in aqueous sodium chloride solution with a high conductivity. The number of discharge starting points, the number of continuous discharges and the amount of bubbles were evaluated as a function of the solution temperature. When the solution temperature was increased from 30 to 56 ℃, the plasma generation rate increased from 19% to 41%, and the number of discharge starting points and the number of continuous discharges increased 1.5 times and 1.3 times, respectively. It was suggested that the increase in plasma generation rate was due to the increase in cavitation bubbles.