Gel electrolytes for quasi-solid dye-sensitized solar cells ͑QDSC͒ are reported. The gel electrolyte consists of ionic liquids and nanoparticles modified with imidazolium cations. Ionic liquid-type gel electrolytes containing nanoparticles are well-known. The difference between previous reports and this report is that imidazolium cations are bonded to nanoparticles through Ti-O-CObonds and long alkyl chains. The role of the long alkyl chains turns out to be critical for high performances. When unmodified nanoparticles are added into ionic liquids until the gel becomes of clay-like hardness, the photovoltaic performances decrease with an increase in the bare nanoparticle content. However, the decreases in photovoltaic performances are retarded when surfacemodified nanoparticles are added. Photovoltaic performances increase with an increase in the chain lengths connecting nanoparticles and imidazolium cations. When the chain length becomes 12 and counter anion is I − , solidification occurs without losing the performance of DSCs having the parent liquid electrolytes. The photocurrents of QDSCs do not decrease even when the ratio ͑nanoparticles/ionic liquids͒ increases to 0.9 and the feature looks like hard clay. Ionic paths between nanoparticles are discussed.Dye-sensitized solar cells ͑DSC͒ contain volatile liquid electrolytes. 1 Therefore, solidification is one of the crucial research items. All solid DSCs containing polymer electrolytes, organic and inorganic hole conductors have been reported previously. 2-10 We took another approach, namely, solidification with gel electrolytes. 11-27 Recently, composite gels consisting of ionic liquidtype electrolytes and nanoparticles have been reported. Gratzel et al. have reported gel electrolytes consisting of ionic liquids and silica nanoparticles. 20,21 Usui et al. have also reported gel electrolytes containing ionic liquids and nanoparticles. 22 They have reported that imidazolium iodides are adsorbed on nanoparticles and ionic paths are fabricated. 22 Kim et al. have reported composite polymer electrolytes containing polyethylene oxides and silica nanoparticles. 23 Recently, we have reported latent gel electrolytes containing nanoparticles and dicarboxylic acids having long alkyl chains. 28 The gelation occurs by the reaction of the nanoparticles with the carboxylic acids. Gratzel et al. have added about 5% of silica nanoparticles into ionic liquid-type electrolytes. 20 Other papers have not described the nanoparticle content clearly. From our experiences, these gels are soft and nanoparticle content is minimized in order not to decrease the short circuit current ͑J sc ͒. Actually, the J sc decreases with an increase in nanoparticle content, as is discussed in this text. Our purpose is to increase nanoparticle content in order to decrease the amount of liquid electrolytes and to bring the gel electrolytes close to solid-state ones. In this paper, we propose a guideline to prepare high-performance clay-like electrolytes having high nanoparticle content for DSCs. We aim...

The experimental evaluation of the wave number and characteristic impedance of stacked-screen regenerators is described. First, a two-by-two transfer matrix of a stacked-screen regenerator was estimated from pressure measurements performed at four different positions; then, the wave number and characteristic impedance of the regenerator were evaluated using a "capillary-tube-based" theory that models a stacked-screen regenerator as an array of pores having a uniform cross section. The evaluation was applied to seven types of stacked-screen regenerators. The experimental results show that these stacked-screen regenerators can be modeled as arrays of circular-cross-section tubes. Moreover, an empirical equation used to estimate the radius of the circular cross section of the tubes comprising the modeled stacked-screen regenerators was addressed.

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N-type Bi 2 Te 2.85 Se 0.15 thermoelectric materials were prepared by liquid phase growth (LPG) using a sliding boat, a simple and short fabrication process for Bi 2 Te 3 -related materials. Cu was selected as a donor dopant, and its effect on thermoelectric properties was investigated. Thick sheets and bars of Cu x Bi 2 Te 2.85 Se 0.15 (x = 0-0.25) of 1-2 mm in thickness were obtained using the process. X-ray diffraction patterns and scanning electron micrographs showed that the in-plane direction tended to correspond to the hexagonal c-plane, which is the preferred direction for thermoelectric conversion. Cu-doping was effective in controlling conduction type and carrier (electron) concentration. The conduction type was p-type for undoped Bi 2 Te 2.85 Se 0.15 and became n-type after Cu-doping. The Hall carrier concentration was increased by Cu-doping. Small resistivity was achieved in Cu 0.02 Bi 2 Te 2.85 Se 0.15 owing to an optimized amount of Cu-doping and high crystal orientation. As a result, the maximum power factor near 310 K for Cu 0.02 Bi 2 Te 2.85 Se 0.15 was approximately 4 9 10 À3 W/K 2 m and had good reproducibility. Furthermore, the thermal stability of Cu 0.02 Bi 2 Te 2.85 Se 0.15 was also confirmed by thermal cycling measurements of electrical resistivity. Thus, n-type Bi 2 Te 2.85 Se 0.15 with a large power factor was prepared using the present LPG process.