Silicon production in a fluidized bed reactor: Final report

Part of the development effort of the JPL in-house technology involved in the Flat-Plate Solar Array (FSA) Project was the investigation of a low-cost process to produce semiconductor-grade silicon for terrestrial photovoltaic cell applications. of silane in a fluidized-bed reactor (FBR). Following initial investigations involving 1and 2-in. diameter reactors, a 6-in. diameter, engineering-scale FBR was constructed to establish reactor performance, mechanism of silicon deposition, product morphology, and product purity. The overall mass balance for all experiments indicates that more than 90% of the total silicon fed into the reactor is deposited on silicon seed particles and the remaining 10% becomes elutriated fines. Silicon production rates were demonstrated of 1.5 kg/h at 30% silane concentration and 3.5 kg/h at 80% silane concentration. The mechanism of silicon deposition is described by a six-path process: heterogeneous deposition, homogeneous decomposition, coalescence, coagulation, scavenging, and heterogeneous growth on fines. The bulk of the grown silicon layer appears to be made up of small diameter particles. This product morphology lends support to the concept of the scavenging of homogeneously nucleated silicon. The process selected was based on pyrolysis Excellent purity of the silicon product was obtained from an FBR equipped with a quartz liner. less than the detection limits of spark source mass spectroscopy (e.g., Fe 5 0.6 ppma, Cr < 0.02 ppma, Zn < 0.04 ppma, Co 5 0.1 ppma). fabricated from this pure silicon product showed encouraging results and the data are described in this report. The product silicon had metallic contaminants Solar cells