Improvement of Crystallinity and Solar Cell Efficiency of Spherical Silicon by Seeding Crystallization Techniques

Silicon spheres were fabricated from melted silicon by dropping method. In order to improve the quality of silicon spheres, we developed a novel seeding crystallization technique for the solidification of silicon droplets in high-speed dropping. High-pure silicon powders were used as seeding source material. They were embedded into the silicon droplets by floating and confining within a specific region on the dropping route. Experimental results demonstrated that this method is very effective on improving the crystalline quality and on reducing the defects and dislocations of the silicon spheres. A solar cell module having about 4x lens concentrator was developed without polishing the spheres. A conversion efficiency of 11.3% under AM1.5, 100 mW/cm² sunlight was achieved from single sphere with size of 1.0 mm in diameter