Development of a method to form hollow silicon spheres, with application to photovoltaic cells: experiment and computation.

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04293
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Ritsumeikan University
• Principal Investigator: WELLS John C. 立命館大学, 理工学部, 教授 (60301644)
• Co-Investigator(Kenkyū-buntansha): 河野 悠 立命館大学, 理工学部, 助教 (40822838)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: Silicon / Hollow spheres / Hollow jet method / Solidification

Outline of Final Research Achievements

Hollow silicon millispheres have been fabricated using a hollow coaxial jet for the first time.
Silicon was melted in a graphite crucible at　1823 K, then ejected from the annulus of a coaxial nozzle as argon gas was injected from an inner nozzle whose inner and outer diameters are 0.4　mm and 1 mm respectively. Sphere diameters were 1 - 2 mm with spherical outer surfaces, and the frequency of formation was approximately 145 Hz.
The wall thicknesses varied gradually between antipodes. The interior surfaces were somewhat non-spherical, with horn-like structures where the　wall was thicker, most likely owing to silicon expansion as solidification finishes. This is the first report of such a “horn expansion　structure” observed on a concave substrate.

Free Research Field

Fluid Mechanics

Academic Significance and Societal Importance of the Research Achievements

Hollow silicon millispheres have been fabricated using a hollow coaxial jet for the first time. It is hoped that such hollow structures could permit higher photovoltaic energy efficiency that the solid spheres that are currently used for spherical silicon solar cells.