Abstract
Cu-In-Se ternary system, especially the CuInSe2 (CIS) compound, is of highest interests to solar cell applications. However, there is very limited information available regarding phase equilibria of the Cu-In-Se ternary system. The liquidus projection of the Cu-In-Se system was experimentally determined in this study. Various ternary Cu-In-Se alloys were prepared with pure elements. Proper amounts of elements were encapsulated in quartz tubes, completely melted and mixed at high temperatures, and then the molten alloys were quenched. Their microstructures were metallographically examined. Compositional analysis and X-ray diffraction analysis were carried out to determine the primary solidification phases of these ternary alloys. The univariant lines of the liquidus projection were constructed based on these experimental results of the Cu-In-Se alloys and the available phase relationships of the three binary constituent systems. The Cu-In-Se ternary system has eleven primary solidification phases: β1-Cu2Se, Cu, β2-Cu4In, γ-Cu9In4, η-Cu2In, Cu11In9, In, In4Se3, InSe, Se and CuInSe2. It also has a large miscibility gap extending from the Cu-Se side to In-Se side and passing through six primary-phase regimes. The temperatures of the invariant reactions were determined by differential thermal analyzer. The CuInSe2 compound, a semiconductor with excellent optoelectronic properties for high efficiency thin film solar cell, was grown by Bridgeman method and its electrical properties were measured as well.