Growth and properties of silicon filaments for photovoltaic applications

Thin silicon filaments were grown from the melt by three different methods: (a) RF-heated float-zone pedestal growth of high-purity, dislocation-free, single-crystal filaments, (b) growth of <1¯1¯2> axis, (111) face, dendrite filaments at high pulling rates from a supercooled melt in a quartz crucible, and (c) capillary die growth of thin-walled, small-diameter Si tube-filaments with high ratio of surface area to volume and concomitant device structure advantages. Minority-carrier lifetime τ was used to assess the filaments. For the three growth methods listed above, values as high as 660 μsec, 53 μsec, and 42 μsec were observed, respectively. Thin silicon filaments with good crystallographic perfection, grown at high speeds, may be useful as active semiconductor elements in multiple linear-concentrator-array PV systems and in other optoelectronic applications