Electrification of Droplet by Applying High-Voltage for Spherical Silicon Solar Cell

Spherical silicon solar cell is solar cell that uses silicon spheres of 1 mm in diameter. Purpose of my research is establishment of a manufacturing technique of the spherical silicon. The spherical silicon is produced by the dropping solidification method: a capillary jet of liquid metal is split into droplets and the droplets are solidified during free fall. Minagawa et al. found that mono-dispersed droplets could be generated by applying an intermittent electromagnetic pinch force to a liquid metal jet. However, the droplets frequently coalesced during free fall before completing its solidification, therefor mono-dispersed spherical silicon could not be obtained. In order to solve this problem, an electrification method was investigated in this study. The droplets are electrified by applying a high voltage. It is expected that a repulsive force will act upon the charged droplets and prevent them from coalescence. Experiments on droplets electrification were carried out with capillary jet of water and liquid gallium. Droplet charges were measured by an electrometer. It was found that the droplet charge depends on some parameters such as a jet diameter, shape of an electrode and a value of applied voltage. The experimental results were compared with a theoretical analysis, which has proposed by Brandenberger et al., and the agreement between the two was quite well. It was concluded that a droplet charge can be estimated by the theoretical model.