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.
Structure and orientation of vacuum-evaporated poly(di-methyl silane) film
Abstract We have succeeded in obtaining the primitive translation vectors of the sub-cell of poly(di-methyl silane) [Si(CH3)2]n crystal. The crystal structure of poly(di-methyl silane) has been clarified by comparing the experimental X-ray diffraction pattern with that of theoretical pattern. The crystal has a monoclinic unit cell (sub-cell) with a=0.745 nm, b=0.724 nm, c=0.389 nm and γ=67.1°. Although poly(di-methyl silane) is the most fundamental polysilane, it is not solved in organic solvents at room temperature. Therefore, the poly(di-methyl silane) thin film has been prepared by a vacuum evaporation technique. In this paper, poly(di-methyl silane) thin films are prepared using new vacuum evaporation system, and the orientation of poly(di-methyl silane) chain has been examined as a function of vacuum pressure as well as substrate temperature during the evaporation. As a result, it is found that the orientation of poly(di-methyl silane) chain is strongly affected not only by the pressure but also by the substrate temperature during the deposition.
Exciton states of polysilanes as investigated by electro-absorption spectra
Abstract Electro-absorption (EA) spectra have been investigated for thin films of poly(di-n-hexylsilane) which shows the thermochromic phase transition associated with the conformational change in Si-backbones. The EA spectra for the trans-planer polysilanes (low-temperature phase) have revealed the one-photon forbidden A g state at 4.2 eV in addition to the Stark-shifted lowest B u exciton at 3.4 eV. The drastic change in EA spectra is observed on the phase transition, which is interpreted as the influence of the backbone conformation on the extended exciton states.