Crystal Structure Analysis of Spherical Silicon Using X-Ray Pole Figures

Abstract

Spherical silicon can be produced directly from melted silicon allowing them to solidify into spherical shape by surface tension; several organizations have carried out trial investigation for fabricate solar cells. Spherical silicon produced by this method are generally polycrystalline and solar cells fabricated from these product are strongly affected by the crystallinity. In this report, an X-ray pole plot analysis of crystal structure of spherical silicon is described. We use pole figure measurement in X-ray diffraction, because distribution and number of the small crystals are directly observable. From (111) pole figure of single crystal as well as polycrystal silicon wafers, we found four poles for the (100) single crystal test sample wafer. In case of the polycrystal, the number of poles is proportional to the number of crystal grains. We have also successfully analyzed the crystallinity of spherical silicon by the pole figure measurement. The (111) pole figure has only four poles in the case of the single crystal spherical silicon. The limitation of sampling position is also discussed.

Crystal morphology of spherical silicon particles produced by jet-splitting method

“…On the surface of group (a) silicon, we can find the horns which are characteristic of Si(1 1 1). We confirmed that the directions of horns are Si(1 1 1) by means of X-ray pole figure analysis [1]. On the surface of group (b), we can find the eruption of silicon due to the volume increase in the transformation process from liquid to solid, which was reported by Jian et al [3].…”

“…The characteristics of surface image, cross-sectional image and X-ray pole figure analysis of those three groups were listed up in Table 1. The distribution and the number of the small crystals are directly measured using X-ray pole figure analysis [1]. In the case of polycrystals, the number of poles is proportional to the number of grains.…”

“…Spherical silicon solar cells (diameter ¼ 1 mm) are expected to be low-cost solar cells because of less silicon consumption per watt compared to conventional crystalline silicon solar cells [1,2]. It is necessary for those cells to produce the spherical silicon particles with good crystallinity at ultra-high speed.…”

Crystal Characterization of Spherical Silicon Solar Cell by X-ray Diffraction

“…We developed a dropping method to fulfill this requirement and succeeded in the extremely high speed production of Si spheres about 1 mm in diameter. 4) Moreover, we proposed a new type of spherical Si solar cell with a semi-concentration reflector system. Therefore, our spherical Si solar cells are expected to be inexpensive, because the quantity of Si spheres decreases.…”

Effects of Hydrogen Passivation for Spherical Silicon Solar Cells Fabricated by Dropping Method

“…We developed a dropping method to fulfill this requirement and succeeded in the high-speed production of Si spheres of about 1 mm in diameter. 4) The Si spheres are generally multicrystalline and include dislocation and point defects possibly caused by the seedless crystal growth during dropping. Processes for improving the crystal quality are necessary for the electrically active crystal defects.…”