Fabrication of Spherical Silicon Solar Cells with Semi-Light-Concentration System

A spherical Si solar cell with a semi-light-concentration system was successfully fabricated using a spherical Si crystal produced by a dropping method. The dropping method has great potential for low-waste and low-cost fabrication because the Si spheres can be made directly from dropping melted Si without the cutting and polishing processes of Si ingots. The fabricated Si spheres were generally multicrystalline due to the crystal growth through homogeneous crystal nucleation in containerless states. Spherical Si solar cells were fabricated using a Si sphere with a diameter of 1 mm as a solar cell substrate and then mounted on a reflector cup with a hexagonal aperture to complete the semi-light-concentration system. The current–voltage (J–V) measurement of the cell demonstrated an energy conversion efficiency of 10.4%. The key parameters for achieving higher efficiency are discussed with J–V data analysis, and quantum efficiency and laser-beam-induced current measurements.