Fabrication of Spherical Silicon Crystals by Dropping Method and Their Application to Solar Cells

Abstract

Spherical Si crystals for solar cell substrates have been successfully fabricated by a dropping method. In the dropping method, melted Si droplets were instilled at normal pressure or in the decompression state (0.5 atm) to control the cooling rate of the spherical Si, dominating crystal quality parameters such as dislocation density in crystal grains. Differences in the crystal quality of the spherical Si crystals were analyzed by surface observation with scanning electron microscopy after Dash etching. Through our baseline process, spherical Si solar cells were fabricated using spherical Si crystals with a diameter of 1 mm fabricated in the decompression state. The current-voltage measurement of the solar cell showed an energy conversion efficiency of 11.1% (short-circuit current density: 24.7 mA/cm 2 , open-circuit voltage: 601 mV, fill factor: 74.6%). These results indicated that spherical Si crystals fabricated by the dropping method have a great potential for the substrate material of high-efficiency and low-cost solar cells.

Construction and characterization of spherical Si solar cells combined with SiC electric power inverter

“…Spherical Si solar cells can reduce the consumption of Si compared with the conventional crystal Si solar cells [12][13][14][15][16][17][18][19][20]. Flexible, light solar cells were also manufactured using silicon spheres with a diameter of ~1 mm with a pn junction [21].…”

A Front-Tracking Method for Three-Phase Computations of Solidification with Volume Change

“…A solidification problem in which there is the presence of solid, liquid and gas appears in many methods of growing crystals from melts such as Czochralski crystal growth (Porrini, 2001), float-zone processing (Markvart, 2000), laser welding (Booth, 2004) and spraying (Minemoto and Takakura, 2007). The three phases meet at the tri-junction, and the solid phase comes directly from the melt.…”

Construction and evaluation of photovoltaic power generation and power storage system using SiC field-effect transistor inverter

“…Consumption of Si can be reduced for the use of spherical Si solar cells, compared with conventional crystal Si solar cells [15][16][17][18][19][20][21][22][23][24]. Flexible and light solar cells were also manufactured using silicon spheres with a diameter of ~1 mm with a pn junction at the sphere surface [24][25][26][27].…”