Atmospheric pressure synthesis of In₂Se₃, Cu₂Se, and CuInSe₂without external selenization from solution precursors

In₂Se₃, Cu₂Se, and CuInSe₂thin films have been successfully fabricated using novel metal organic decomposition (MOD) precursors and atmospheric pressure-based deposition and processing. The phase evolution of the binary (In-Se and Cu-Se) and ternary (Cu-In-Se) MOD precursor films was examined during processing to evaluate the nature of the phase and composition changes. The In-Se binary precursor exhibits two specific phase regimes: (i) a cubic-In_xSe_yphase at processing temperatures between 300 and 400 °C and (ii) the γ-In₂Se₃phase for films annealed above 450 °C. Both phases exhibit a composition of 40 at.% indium and 60 at.% selenium. The binary Cu-Se precursor films show more diverse phase behavior, and within a narrow temperature processing range a number of Cu-Se phases, including CuSe₂, CuSe, and Cu₂Se, can be produced and stabilized. The ternary Cu-In-Se precursor can be used to produce relatively dense CuInSe₂films at temperatures between 300 and 500 °C. Layering the binary precursors together has provided an approach to producing CuInSe₂thin films; however, the morphology of the layered binary structure exhibits a significant degree of porosity. An alternative method of layering was explored where the Cu-Se binary was layered on top of an existing indium-gallium-selenide layer and processed. This method produced highly dense and large-grained (>3 µm) CuInSe₂thin films. This has significant potential as a manufacturable route to CIGS-based solar cells.