Masaru Sakamoto

Bio: Masaru Sakamoto is an academic researcher from Kyoto University. The author has contributed to research in topics: Dye-sensitized solar cell & Titanium oxide. The author has an hindex of 4, co-authored 4 publications receiving 1837 citations.

Determination of parameters of electron transport in dye-sensitized solar cells using electrochemical impedance spectroscopy.

Abstract: The same equation was derived from two different impedance models based on the quite different physical descriptions proposed by Kern et al.(1) and by Bisquert.(2,3) Reliable values of the parameters relating to electron transport in dye-sensitized solar cells can be determined from measured spectra by electrochemical impedance spectroscopy when careful analysis of the measured spectra is done based on the classification and clarification of the same impedance equation consequent from the two models. The requisites for making highly efficient dye-sensitized solar cells were proposed.

Highly Efficient Dye-Sensitized Solar Cells with a Titania Thin-Film Electrode Composed of a Network Structure of Single-Crystal-like TiO2 Nanowires Made by the “Oriented Attachment” Mechanism

Abstract: In this study, single-crystal-like anatase TiO(2) nanowires were formed in a network structure by surfactant-assisted self-assembling processes at low temperature. The crystal lattice planes of the nanowires and networks of such wires composed of many nanoparticles were almost perfectly aligned with each other due to the "oriented attachment" mechanism, resulting in the high rate of electron transfer through the TiO(2) nanonetwork with single-crystal-like anatase nanowires. The direction of crystal growth of oriented attachment was controlled by changing the mole ratio of acetylacetone to Ti, that is, regulating both the adsorption of surfactant molecules via control of the reaction rate and the surface energy. A single-crystalline anatase exposing mainly the [101] plane has been prepared, which adsorbed ruthenium dye over 4 times higher as compared to P-25. A high light-to-electricity conversion yield of 9.3% was achieved by applying the titania nanomaterials with network structure as the titania thin film of dye-sensitized solar cells.

Preparation of Nanocrystalline TiO2 with Mixed Template and Its Application for Dye-Sensitized Solar Cells

Abstract: This work describes a procedure based on a mixed template of copolymer F127 [poly(ethylene oxide) 106 -poly(propylene oxide) 70 -poly(ethylene oxide) 106 ] and surfactant CTAB (cetyltrimethylammonium bromide) for generating anatase TiO 2 nanocrystals. When the particle size is 3-5 nm, the surface area without aggregation is about 300 m 2 /g, but our experimental value is 180 m 2 /g. This means that not all surfaces of 3-5 nm particles are exposed. Then the prepared TiO 2 nanocrystals were used to assemble dye-sensitized very thin solar cells of about 6 μm. Its photocurrent-voltage performance was investigated. The mixed template allowed the fabrication of crack-free porous TiO 2 film electrodes of various thicknesses by repetitive coating and calcinations. The transparent solar cell obtained with a six-time repetitive coating exhibited an open-circuit potential of V oc = 760 mV; a short-circuit photocurrent density, J sc = 17.2 mA/cm 2 ; a fill factor, ff = 0.635; and an efficiency of η = 8.3%. A solar cell using the commercial P25 as the TiO 2 film electrode was also assembled for comparison, and the result are analyzed and discussed.

Colloidal nanocrystal synthesis and the organic–inorganic interface

Abstract: Colloidal nanocrystals are solution-grown, nanometre-sized, inorganic particles that are stabilized by a layer of surfactants attached to their surface. The inorganic cores possess useful properties that are controlled by their composition, size and shape, and the surfactant coating ensures that these structures are easy to fabricate and process further into more complex structures. This combination of features makes colloidal nanocrystals attractive and promising building blocks for advanced materials and devices. Chemists are achieving ever more exquisite control over the composition, size, shape, crystal structure and surface properties of nanocrystals, thus setting the stage for fully exploiting the potential of these remarkable materials.

Combined Experimental and DFT-TDDFT Computational Study of Photoelectrochemical Cell Ruthenium Sensitizers

Abstract: We report a combined experimental and computational study of several ruthenium(II) sensitizers originated from the [Ru(dcbpyH2)2(NCS)2], N3, and [Ru(dcbpyH2)(tdbpy)(NCS)2], N621, (dcbpyH2 = 4,4‘-dicarboxy-2,2‘-bipyridine, tdbpy = 4,4‘-tridecyl-2,2‘-bipyridine) complexes. A purification procedure was developed to obtain pure N-bonded isomers of both types of sensitizers. The photovoltaic data of the purified N3 and N621 sensitizers adsorbed on TiO2 films in their monoprotonated and diprotonated state, exhibited remarkable power conversion efficiency at 1 sun, 11.18 and 9.57%, respectively. An extensive Density Functional Theory (DFT)−Time Dependent DFT study of these sensitizers in solution was performed, investigating the effect of protonation of the terminal carboxylic groups and of the counterions on the electronic structure and optical properties of the dyes. The calculated absorption spectra are in good agreement with the experiment, thus allowing a detailed assignment of the UV−vis spectral features ...

Colloidal nanocrystal synthesis and the organic-inorganic interface - eScholarship

Abstract: Colloidal nanocrystals are nanometer-sized, solution-grown inorganic particles stabilized by a layer of surfactants attached to their surface. The inorganic cores exhibit useful properties controlled by composition as well as size and shape, while the surfactant coating ensures that these structures are easy to fabricate and process. It is this combination of features that makes colloidal nanocrystals attractive and promising building blocks for advanced materials and devices. But their full potential can only be exploited if we achieve exquisite control over their composition, size, shape, crystal structure and surface properties. Here we review what is known about nanocrystal growth and outline strategies for controlling it.

Semiconductor nanowires for energy conversion.

Abstract: Semiconductor nanowires represent an important class of nanostructure building block for photovoltaics as well as direct solar-to-fuel application because of their high surface area, tunable bandgap and efficient charge transport and collection. In this talk, I will highlight several recent examples in this lab using semiconductor nanowires and their heterostructures for the purpose of solar energy harvesting. In addition, we have also discovered that the thermoconductivity of the silicon nanowires can be significantly reduced due to phonon scattering, pointing to a very promising approach to design better thermoelectrical materials. It is important to note that the engines that generate most of the world's power typically operate at only 30–40 per cent efficiency, releasing roughly 15 terawatts of heat to the environment. If this “wasted heat” could be recycled, the impact globally would be enormous. Our silicon nanowire thermoelectric technology could have a significant impact in alternative energy generation.