| Assessment of the thermochemistry and phase equilibrium data of the Cu-Se binary and Cu-In-Se ternary systems was performed to suggest the phase diagrams. Sub-lattice models were used to describe the Gibbs energy of the condensed solutions. Coupled with previously reported assessments, the Cu-Ga-In phase diagram was predicted by extrapolation of the Cu-Ga, Cu-In and Ga-In binary systems. Ternary interaction parameters were and subsequently added to achieve consistency with recent ternary experimental data.; In situ high-temperature X-ray diffraction technique was used to investigate the reaction pathways and phase evolution of binary Cu-Se, In-Se and Ga-Se compounds prepared as an intimate mixture or bi-layer. The results revealed that the overall phase transformation of binary metal (Cu, In and Ga)-Se compounds qualitatively follows the sequence predicted by the phase diagram, but the detailed reaction path of each binary compound depends on the as-deposited precursor structure and phases produced during the deposition process.; Reaction pathways and kinetics of polycrystalline alpha-CuInSe 2 (CIS), CuGaSe2 (CGS), and Cu(In,Ga)Se2 (CIGS) formation were also systematically investigated using in situ high-temperature X-ray diffraction during thermal annealing of stacked bilayer and intimately mixed monolayer precursors, and selenization of elementally mixed metal precursors. The lowest temperature to form CIS was identified as ∼140°C, which was achieved by thermal annealing of intimately mixed Cu-In-Se precursor. Formation temperatures of CGS (i.e. 260 to 300°C) were relatively higher than those of CIS (i.e. 140 to 250°C) and CIGS (i.e. 260°C). MoSe2 formation was always clearly observed during selenization and for CIS, only after complete formation of CIS. Quantitative analysis of time-resolved X-ray diffraction data by adopting the Avrami and parabolic rate models provided reaction order, rate constant, and activation energy.; DICTRA simulation of CIS formation by selenization of a Cu-In precursor was performed using the kinetic results obtained by time-resolved, in situ HTXRD experiments along with the thermodynamic description of the CIS system. The target reaction system was simplified as a pseudo-binary reaction, CuIn + 2Se → CuInSe2, for which the reliable mobility parameters for Se transport in CIS were obtained. |
