The flat glass industry successfully commercialized pyrolytically deposited low emissivity glass based on color-suppressed fluorine-doped tin oxide in 1990. The current production capability of this product approaches 500,000 m2 of coated glass per year. Spin-off products for the photovoltaic (PV) industry were introduced by LOF in 1991 and enjoy considerable success in this emerging technology. Many PV researchers, however, still prefer to produce optimized tin oxide off-line in CVD furnaces as they can be produced on higher performing but higher cost substrates. In this paper, we discuss the characteristics of on-line production of PV transparent conductors (TCO), including the tradeoffs required when a coating process is incorporated onto a float glass line. We conclude by suggesting that eventual large scale commercialization of thin film photovoltaics dictates the use of on-line TCO based on economics, the excellent uniformity and repeatability, and ready availability. We believe that the PV researchers are best served by understanding the capabilities of on-line tin oxide production, and tailoring their programs towards the characteristics of these new cost effective TCOs.

The atmospheric pressure thermal decomposition of disilane to produce a Si:H films was studied between 450 and 520° C in a laminar flow reactor. The structural properties of the films exhibited a strong dependence not only on substrate temperature but also on reactor flow position. Films deposited at higher substrate temperatures had less dihydride bonding in the films while the monohydride bonding remained relatively constant. Despite a decrease in the total hydrogen content of the films as the deposition temperature increased from 450 to 500° C, the AM1 photoconductivity increased over an order of magnitude and the hole diffusion length of the films doubled. In addition to the changes in structural and electrical properties as a function of substrate temperature, variations in these properties were also observed as a function of flow position. At early flow positions the amount of dihydride bonding in the films was small and the AM1 photoconductivity and hole diffusion lengths of the films increased. The flow dependence of the film properties is explained by changes in the film precursors due to the evolution of the gas phase chemistry.