Polycrystalline silicon film and solar cells by FBR-CVD

Solar industry growth and a silicon feedstock shortage have spurred interest in thin silicon film photovoltaic (PV) technology. To reduce PV panel and electricity cost, technologies are needed with high deposition rates of high-quality Si film, scalability to large areas and integrated cell and panel fabrication. A new SRI International deposition technology based on fluidized bed reactor-chemical vapor deposition (FBR-CVD) takes advantage of the high heat and mass transfer in a FBR, and combines it with subhalide CVD chemistry with highly reactive species created in the reactor. The SRI´s FRB design minimizes boundary layer thickness to achieve deposition rates as high as several microns per minute and good coating uniformity. The resulting silicon films are highly crystalline with 10-100 μm grain sizes over 5 cm²; with in-depth homogeneous resistivity, typically 0.1-5 Ω·cm, but up to 1000 Ω·cm obtained under some deposition conditions; and with bulk diffusion length >200 μm. The reactor configuration can be used for continuous and integrated cell/panel fabrication.