Progress on crystalline silicon thin film solar cells by FBR-CVD: Effect of substrates and reactor design

Thin film polycrystalline solar cells on low cost substrates offer an attractive path to large scale production of solar cells with the potential to generate electricity at 1$/W. SRI International has a propriety technology to deposit Si films in a reactor based on fluidized bed technology. The results presented in this paper show that, with a proper reactor design, Si films can be grown at rates of 7 μm/min and higher. Films are crystalline, with crystallite sizes higher than 20 μm. We have also evaluated the performance of SiO₂ diffusion barriers as a potential way towards the use of low cost substrates, such as metallurgical grade Si. Whereas SiO₂ layers of 0.1 μm are not sufficient to stop P diffusion from the substrate to the film, 0.7 μm layers are thick enough to accomplish this goal. The reactor configuration can be used for continuous and integrated cell/panel fabrication. At present we are building a first continuous reactor, and in this paper we present some preliminary considerations.