Study of vacuum-evaporated poly(di-methyl silane) thin film and its application to dye-sensitized solar cell
Organopolysilanes are expected to be used for future optical and electronic devices. Poly(di-methyl silane), [Si(CH/sub 3/)/sub 2/]/sub n/, the most fundamental organopolysilane, is not solved in organic solvent at room temperature. Therefore, we have proposed the vacuum evaporation technique in order to obtain thin films of poly(di-methyl silane). In this paper, optical and electrical properties of poly(di-methyl silane) thin films are examined. As a result, it is found that the electric conductivity parallel to the Si backbone is larger by about three orders of magnitude than that perpendicular to the Si backbone. Moreover, highly oriented poly(di-methyl silane) thin film prepared by the vacuum evaporation technique is applied to the dye-sensitized solar cell, and we have succeeded in fabricating the perfectly solid-state dye-sensitized solar cell using poly(di-methyl silane) thin film.
Crystal structures of poly(di-ethyl silane) and poly(di-n-propyl silane)
The packings of the poly(di-ethyl silane) and poly(di-n-propyl silane) crystals have been examined by comparing the experimental X-ray diffraction pattern with the theoretical pattern. The silicon backbone conformation of both crystal is all trans, and the side-chain conformation is mostly determined by the intramolecular steric hindrance. The molecules are closely packed in both cases, and the intermolecular distance is well explained by considering the van der Waals radii of the CH2 and CH3 groups.
Structure and optical properties of ternary Si:C:H films prepared by evaporation of organo-polysilane
Ternary Si:C:H films are prepared by evaporating per-methyl-polysilane powder. The structure and optical properties of the films obtained are examined by various techniques. From infrared absorption and X-ray diffraction measurements, it is found that the film prepared at 27 degrees C contains a large number of Si backbones with an alternating trans-gauche conformation. The ultraviolet absorption spectrum shows a large peak at 300-350 nm and also supports the existence of one-dimensional Si chains. On the other hand, the film prepared at 300 degrees C contains a large number of helical backbones and shows a narrow absorption band at 300 nm. The strength of this absorption band strongly depends on measurement temperature, suggesting excitonic absorption.