First-Principle Study on p-n Control of PEDOT-Based Thermoelectric Materials by PTSA Doping.

PEDOT: Tos, a PSS-free PEDOT-based material, is a promising possible organic thermoelectric material for a practical conversion module because the material reportedly has a large power factor. However, since PEDOT:Tos is mainly reported to be a p-type thermoelectric material, the development of PSS-free PEDOT with n-type thermoelectric properties is desirable. Thus, in order to search for PSS-free PEDOT with n-type thermoelectric properties, we investigated the doping concentration of PTSA dependence of the thermoelectric property using the first-principle calculation. The band structure and the density of state indicated that the n-type thermal electromotive force was attributed to the electrons' large effective mass. Such electrons were produced thanks to the binding of the dopant PTSA to the benzene ring. The contribution of the electron to the Seebeck coefficient increased with increasing PTSA doping concentrations.

Effect of Boron in a Hierarchical Nanoporous Layer Formation on Silicate Glass.

A hierarchical nanoporous layer (HNL) can be formed on the silicate glass surface by simple alkali etching. Though it reportedly exhibits various useful functions, such as superhydrophilicity, optical anti-reflection, and material impregnation, the principle of its formation still remains unclear. In this study, HNL formation behavior was experimentally investigated while using scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) to clarify the role of boron contained in glass. As a result, it was found that HNL formation was significantly promoted by boron, which was rapidly eluted prior to alkali and alkaline earth metals. This suggests that boron, which forms the skeleton structure of glass together with Si and O, elutes to partially decompose the skeleton, and extends the elution route for HNL formation.

A New Composite Structure of PEDOT/PSS: Macro-Separated Layers by a Polyelectrolyte Brush.

Polyethylene dioxythiophene and polyethylene sulfonic acid (PEDOT/PSS) composite is gathering attention as an organic transparent conductive film material. However, it requires a core-shell structure in which conductive PEDOT is covered with insulating PSS. Providing film formability and a carrier to PEDOT, the PSS shell hinders carrier conduction as an insulating barrier. In this study, we realized that creating a macro-separated PEDOT/PSS composite by using a polyelectrolyte brush substrate and in-situ PEDOT polymerization without the PSS barrier increases durability and conductivity in comparison with commercially available PEDOT/PSS film, achieving a conductivity of 5000-6000 S/cm.

p-n Control of AlMgB14-Based Thermoelectric Materials by Metal Site Occupancy.

The mechanism for the p-n control of AlMgB14-based thermoelectric material was investigated using Rietveld refinement and the first principle calculation. The p- and n-type AlMgB14-based thermoelectric materials were prepared by spark plasma sintering (SPS) with changing raw powder mixture ratio. Temperature dependence of Seebeck coefficient and electrical conductivity were different between the two types of samples. Seebeck coefficient shifted from positive to negative with increasing the number of valence electrons in the metal sites calculated by the metal site occupancy. The density of states and electron density distribution indicated that the electrons transfer from metal atoms to the B atoms.

Hierarchical nanoporous glass with antireflectivity and superhydrophilicity by one-pot etching.

We have developed a hierarchical nanoporous layer (HNL) on silicate glass by a simple one-pot etching method. The HNL has a three-dimensionally continuous spongelike structure with a pore size of a few tens of nanometers on its apparent surface. The pore size gradually decreases from the apparent surface to the HNL-bulk interface. This HNL bestows significant properties to glass: low optical reflectivity that reflects 7% less visible light than nontreated glass and long-persistence superhydrophilicity that keeps its water contact angle at about 5° for more than 1 year. The superhydrophilicity also realizes antifogging and antifouling functionalities.

Femtosecond fluorescence dynamics imaging using a fluorescence up-conversion microscope.

Femtosecond fluorescence dynamics imaging microscopy was performed. Femtosecond fluorescence dynamics images were constructed based on the "mean" fluorescence decay or rise time constants that were evaluated by the time-resolved intensity sampling using a fluorescence up-conversion microscope. This dynamics imaging microscopy was carried out for the organic microcrystals alpha-perylene and tetracene-doped anthracene microcrystal, and ultrafast dynamics in the organic microcrystals were clearly imaged in the two-dimensional manner. For the alpha-perylene microcrystal, the obtained dynamics images showed that the crystal edges exhibited relatively shorter free exciton and the Y-state lifetimes compared to the crystal center, reflecting the higher concentration of defects. For the tetracene-doped anthracene microcrystal, the image was constructed based on the time constant of excitation energy transfer from anthracene to tetracene. By experiments changing the doping ratio of tetracene in anthracene, it was concluded that the inhomogeneity observed in the dynamics image arises from the difference in the local concentration of tetracene in the mixed crystal.

Merging of alpha and slow beta relaxation in supercooled liquids.

Dielectric relaxation spectroscopy (1 Hz - 20 GHz) has been performed on supercooled glass-formers from the temperature of glass transition (T(g)) up to that of melting. Precise measurements particularly in the frequencies of MHz order have revealed that the temperature dependences of secondary beta relaxation times in well above T(g) deviate from the Arrhenius relation below T(g): the beta process does not merge with the alpha process around the dynamical crossover temperature in contradiction to previously speculated extrapolations.