Kenji Todori

Investigation of the organic solar cell characteristics for indoor LED light applications

We report an experimental study on the current–voltage characteristics of organic solar cells (OSCs) under indoor light illumination. A daylight color light-emitting diode (LED) was used as the indoor light source. We investigated the short circuit current density, open circuit voltage, and fill factor of the OSC under LED irradiation and compared them with those for a crystal silicon solar cell (c-Si-SC), which occupy a large part of the solar cell market. We found that compared with the c-Si-SC, the OSC had higher power conversion efficiency (PCE). We also derived the maximum feasible PCE of an OSC for indoor applications and calculated that a PCE value of 21.3% could be obtained under daylight color LED illumination at approximately 200 lx. From the results of the calculation, it became apparent that the open circuit voltage plays an important role in achieving a high PCE from OSCs, indicating they are promising as electrical energy harvesting module for indoor applications.

The effect of boundary thermal resistance on HD DVD-ARW optical recording media

Thermal conductivities and boundary thermal resistances of thin films having the thickness of the order of ten nanometers were measured by using the thermo-reflectance method at room temperature. A thermal simulation of HD DVD-ARW (the next-generation advanced rewritable DVD) media was carried out to clarify the effect of boundary thermal resistance at the interface of those films. The thermal conductivity of thin films greatly depends on film thickness. The result of the thermal simulation depends significantly on whether the boundary thermal resistance is considered or not. Thus it is important to consider the boundary thermal resistances and using thermal properties of thin films to perform more accurate calculation for the phase change recording media. The results of the thermal simulation also suggested that the boundary thermal resistances dominate the thermal diffusion and response of the medium.

Formation of pseudo one-dimensional photonic band in visible region by grating pair method

We have succeeded in fabricating a pseudo one-dimensional photonic band system in the visible region using two facing gratings. The transmittance spectra of 3600 and 1800 grooves/mm grating pairs were measured. The results, along with calculations of one-dimensional photonic bands, show that a photonic band exists and the band edges are near 530 THz.

Fabrication of metal core and organic shell nanoparticle packing film for plasmon polariton waveguide

Core-shell Au nanoparticles were synthesized for chemical reaction under mild liquid phase condition. The nanoparticles film was fabricated on a glass substrate for surface plasmon polariton waveguide. The nanoparticle piled up on the substrate made a smooth surface. A waveguide was easily fabricated by the lift-off method and the patterned trench filled method.

Similarities and differences of phonon modes in silicon materials depending on dimension: Raman spectroscopy of polysilanes and siloxene

Abstract We studied the -Si Si- oscillations of all-trans-type polysilanes (poly(di-n-hexylsilane) and poly(di-n-butylsilane) at high pressure) and siloxene by Raman scattering spectroscopy. These are one- and two-dimensional silicon crystals. In these compounds, Raman peaks observed at less than 600 cm−1 corresponded to phonon modes at the Brillouin zone center and boundary of the three-dimensional silicon crystal (c-Si). In these polysilanes, the peaks corresponding to both optical and acoustic modes of c-Si have appeared, but in siloxene only the peaks corresponding to the optical phonon modes have been observed.

Wavenumber shift of more than 20 cm−1 on CO vibration spectrum caused by conformational difference on polymorph in 2-cyano-3-(3,4-methylenedioxyphenyl)-2-propenoic acid

Abstract X-ray analysis of two polymorphs of 2-cyano-3-(3,4-methylenedioxyphenyl)-2-propenoic acid ethyl-ester revealed the difference of cis—trans conformation of cyano group to carbonyl group through the fixed single bond. This difference affected the carbonyl group to the extent of 20 cm −1 shift in vibration and Raman spectrum.

Determination of Organic Crystal Orientation in Glass Capillaries by Microscopic Raman Spectroscopy

Crystallographic axis orientation of 2-cyano-3-(3,4-methylene dioxy phenyl)-2-propenoic acid ethyl ester (CMPE) in a glass capillary with a 10-µm-diameter core was successfully clarified by polarizing microscopic Raman scattering spectroscopy. Polymorphic crystals of CMPE could also be distinguished in the glass capillaries by use of this method.

Slow/Rapid Diffusion of Arsenic in SiO2

The As diffusion in SiO2 had been investigated by using AsSG film. As diffusivities and chemical states in SiO2 are different for N2 and H2+N2 annealing anbients. In N2, the chemical state is not changed from that of as deposited film, and it is the oxidized state with a large diffusivity. On the contrary, As has been changed to the reduced state with a small diffusivity by a H2+N2 annealing. This chemical state transition is a reversible reaction. The diffusion mechanism is assumed to be a substitutional change with Si atoms of the SiO2 network for the oxidized state As and an interstitial diffusion for the reduced state As.