Akio Takahashi

Characteristics of Schottky barrier solar cells using polyacetylene, (CH)x

Abstract We have constructed Schottky barrier solar cells using semiconductive polyacetylene, and investigated their characteristics which are influenced significantly by the surface conditions of the polyacetylene films. The surface contacting the glass wall during polymerization has greater trap density, and the device having a Schottky barrier on the surface shows inferior characteristics to that having a barrier on the other surface. The energy conversion efficiency was improved up to 1%, when the incident light intensity was 7 mW/cm 2 and the energy of 0.2 mW/cm 2 was input into the barrier region through the Al electrode. From the strong dependence of the photovoltaic current on the backward biasing voltage, it is inferred that excitons contribute to the photocarrier generation.

Magnetoresistance and thermoelectric power studies of metal-nonmetal transition in iodine-doped polyacetylene

Abstract Highly conducting polyacetylene iodine-doped to saturation level changed from metallic to nonmetallic states by aging, judging from the temperature dependence of the resistivity. During this change, the thermoelectric power did not vary drastically, suggesting that the transition cannot be ascribed to the change in carrier concentration. By contrast the magnetoresistance changed remarkably on crossing the transition. The transition is ascribed to the effect of disorder.

A Schottky Barrier Type Solar Cell Using Polyacetylene

Schottky barrier type solar cells have been fabricated using polyacetylene, (CH)x as the semiconductive material. Under illumination from a tungsten lamp source (40 mW/cm2), Vsc0.4 V, Joc40 µA/cm2 and F.F.0.25 were obtained. The energy conversion efficiency is estimated to be 0.2% relative to the energy absorbed within the depletion region.

Low-temperature magnetoresistance of heavily FeCl3-doped polyacetylene: Hopping conduction among localized states with Coulomb correlation

Abstract The positive magnetoresistance of disordered fully-FeCl 3 -doped polyacetylene showed a pronounced maximum near 2 T below 4.2 K. This contrasts with the magnetoresistance for disordered I 2 -doped sample showing a dull maximum. The results are analyzed in terms of the magnetic field effect to the hopping conduction among Anderson-localized states with Coulomb correlation. The difference by the dopant species is ascribed to the depth of the Fermi level from the mobility edge.

Polymeric Product of Carbon Disulfide and Its Electrical Properties

The polymeric product of carbon disulfide (CS2) was obtained at normal pressure below room temperature by chemical polymerization with anionic catalyst. This product is very similar to CS2 polymer obtained by conventional method using a high pressure technique (55 kilobars), inferring from the results of IR measurement. The conductivity can be increased to 10-2~10-3S/cm with ammonia and iodine doping. The structure is discussed from the results of XPS measurement.

Optical Transfer Function of Concave Grating Spectrometer Based on Wave Optical Method

Optical transfer functions (OTF) of two types of spectrometer – Eagle mounting and Seya-Namioka mounting – are calculated by the wave-optical method which defines the OTF as the autocorrelation function of the pupil. Results obtained are compared with previous results of the present authors and interpreted as effects of diffraction and aberration on the broadening of point image. The OTFs are calculated also by Fourier transformation of the intensity distribution of point image and compared with those obtained by the first method.

Polarized resonance Raman scattering of iodine-doped polyacetylene with high conductivity

Abstract We investigated the structure and alignment of iodine dopant in the highly conducting polyacetylene (HCPA) with different doping concentration by using polarized resonance Raman spectroscopy (PRRS). It was found for the first time that the I 3 − species is predominant in the highly stretched HCPA film even for the highly doping level ((CHI 0.25 ) x ), in contrast with traditional polyacetylene. We also observed that the intensity ratio of I 3 − /I 5 − and the orientation of I 3 − species increase greatly with increasing initial draw ration of the polyacetylene films.

High electric field effect on the conductivity of iodine-doped polacetylene

Abstract The conductivities of iodine-doped new polyacetylenes with room-temperature values of 7.7 × 10 3 S/cm and 2.6 × 10 4 S/cm were measured as a function of applied electric field in the temperature range of 77 K to 4.2 K. It is shown that the behavior deviated obviously from the Sheng model which has been widely adopted in explaining temperature dependence for conventional polyacetylene with lower conductivity.

Structure and Electric Conductivity of Vapor Deposition Products of Cyano Acetylene

Abstract Cyanoacetylene can be polymerized from vapor state onto an inactive surface of substrate at a temperature as low as 200°C. The structure and electric conductivity of these cyanoacetylene products have been investigated.

Low-temperature magnetoresistance in fully-doped polyacetylene with disorder

Summary form only given. The electrical conductivity of the doped polyacetylene has been improved dramatically by recent synthesis [1]. It is worthwhile to revisit the physical properties with this new polyacetylene. We have taken up fully I/sub 2/-doped and FeCl/sub 3/-doped polyacetylene to get metallic conduction even at low temperature. We found, however, that the highly conductive fully doped polyacetylene changed from metallic to nonmetallic by room-temperature aging due to Anderson localization. For this change, low temperature magnetoresistance changed from negative to positive on crossing the transition. The field dependences of the resistance are qualitatively different for the I/sub 2/-doped and the FeCl/sub 3/-doped. The results are successfully explained in terms of the magnetic field effect to the hopping conduction among Anderson-localized states with Coulomb correlation. The difference by the dopant species is ascribed to the depth of the Fermi energy from the mobility edge. The temperature and magnetic field dependences found in the fully doped case are distinguished from lightly doped case characterized by the Coulomb gap.