Silicon coating of ceramic substrates for low cost solar cell applications

Abstract

Mullite ceramic substrates were coated with silicon using a unique method of growth designed to produce low-cost material suitable for terrestial based solar cell applications. Pieces of mullite were carbon coated on one side and then dipped into molten silicon. The silicon wet the mullite only where the carbon was applied. Directional solidification occurs upon withdrawal. The film thicknesses were reasonably uniform over the area and could be controlled by varying the melt temperature and withdrawal rate, with higher temperatures and faster pull rates giving thinner films. Typical thicknesses of dip coated layers ranged between 20 and 150ym. The layers consist of large elongated grains aligned in the direction of withdrawal. The mullite substrates are slowly dissolved by the molten silicon resulting in some contamination of the silicon layers upon solidification. Glassy carboncoatings were found to be essentially impervious to the molten silicon and prevented dissolution of the substrate even after one hour of immersion. Cells of 1 cm2 active area having JSC