Liquidus projection of Cu–In–Se photovoltaic material system

Abstract

Cu–In–Se (CIS) and its based alloys are among the most important solar cell materials. However, there are only limited Cu–In–Se phase equilibria data available. This study determines the liquidus projection of the Cu–In–Se system. Cu–In–Se alloys were prepared from pure constituent elements. The primary solidification phases of as-cast Cu–In–Se alloys were determined. The univariant lines of Cu–In–Se liquidus projection were constructed according to the experimental results determined in this study, those in the literature and the phase diagrams of its three binary constituent systems. There are 15 primary solidification phases in the ternary Cu–In–Se liquidus projection: β1-Cu2Se, Cu, β2-Cu4In, γ-Cu7In3, η′-Cu2In, Cu11In9, In, In4Se3, InSe, In6Se7, In2Se3, Se, CuSe2, CuSe and CuInSe2 phases. A large miscibility gap extends from the Cu–Se side to the In–Se side. There are 16 ternary invariant reactions in this Cu–In–Se liquidus projection involved in the liquid phase. The temperatures of invariant reactions were determined using differential thermal analysis.