Phase diagram of the CulnSe2-CuGaSe2 pseudobinary system studied by combined ab initio density functional theory and thermodynamic calculation

The phase diagram of the CuInSe2-CuGaSe2 pseudobinary system was determined using a combination of special quasirandom structure approach, ab initio density functional theory calculations, and thermodynamic modelling. It is shown that the CuIn1−xGaxSe2 solution phase has a tendency to phase separation at low temperature. The calculated consolute temperature is 485 K. It is found that both the binodal and spinodal curves are significantly asymmetric and on both curves there are a local maximum and a local minimum, which have not been reported in the previous studies. Our phase diagram can well explain the finding that the inhomogeneity of CuIn0.25Ga0.75Se2 is higher than that of CuIn0.75Ga0.25Se2 at the same temperature, while the previous phase diagrams cannot. Hence, our phase diagram should be more reliable and applicable