Seed-assisted growth of high-quality multi-crystalline silicon in directional solidification

An approach to grain control using seed-assisted growth in directional solidification (DS) is reported in this paper. Proper multi-crystalline silicon seeds at the bottom of the crucible provided numerous fine nucleation points for the controlled grain growth in an optimized hot-zone. Low dislocation density was observed with large numbers of uniform small grains in the silicon ingot, although the grain size increased with crystal growth. Crystals produced using seed-assisted growth showed a higher and more uniform minority carrier lifetime with a much lower dislocation multiplication rate. A higher average solar cell conversion efficiency of about 0.5% in absolute value was obtained in the seed-assisted grown silicon in comparison with that in the seedless silicon under the same cell fabrication process.