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

Abstract

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.

In situ observations of crystal growth of spherical Si single crystals

“…Several cost reduction efforts have been carried out thus far primarily through the reduction of the Si wafer thicknesses, i.e., Si material volume per watt. From the viewpoint of cost reduction, spherical Si solar cells are very attractive because of the expected low-waste and low-cost fabrication features [2][3][4][5]. The advantage of fabricating spherical Si crystals using a dropping method is that the Si crystals can be fabricated directly from dropped molten Si without involving any cutting process which is always required in the fabrication of crystalline Si wafers.…”

Development of Flexible Cu(In,Ga)Se2 Thin Film Solar Cell by Lift-Off Process

“…External quantum efficiency (EQE) measurements of the AC mode were performed at 25˚C under white light bias (~0.3 sun) conditions. The laser-beam-induced current (LBIC) method using the laser diode (: 783 nm, laser power: 0.3 mW) was performed to investigate a spatial distribution of an EQE (Minemoto et al, 2005). In LBIC measurements, a nominal spot size is less than 50 m and a scan step is 53 m.…”

High Temperature In-situ Observation of Si on the Porous Ceramic Substrate Repelling Si Melt for Growth of Spherical Si Crystal

“…Growth technique of shaped Si crystal without cutting process has been remarkably investigated to fabricate lowcost Si solar cells [15]. Some of these studies focus on spherical Si due to its conservation of Si material and reduction of Si consumption per unit electric power generation to less than 1/5 that of wafers because cutting process is not required to fabricate spherical Si crystals [4,5]. Spherical Si is currently produced by droptube method [6].…”