Influence of the stacking order on structural features of the Cu-In-Ga-Se precursors for formation of Cu(In,Ga)Se₂ thin films prepared by thermal reaction of InSe/Cu/GaSe alloys to elemental Se vapor and diethylselenide gas

A novel partway for the fabrication of copper-indium (gallium) diselenide has been developed. This two-stage process consists of the formation of Cu-In-(Ga)-Se precursors and subsequent selenization to form CuIn(Ga)Se ₂. In this work, we have investigated and compared the possible interactions in Cu-In-Ga-Se systems, using sequentially stacked precursors premixed with Se, in order to get a better understanding of the Cu(In,Ga)Se ₂ thin film formation. Comparison of these SEM micrographs clearly revealed that the surface morphologies and hence surface roughness of the resulting Cu(In,Ga)Se₂ absorber films were significantly influenced by the structure of the precursor films prior to selenization. XRD analyses revealed the presence of a graded CuIn_1-xGa_xSe structure, irrespective of the stacking order during the precursor formation step for samples selenized using elemental Se vapor. It was established that distinct from the case of using Se vapor, a single-phase Cu(In,Ga)Se₂ films were obtained by diethylselenide (DESe) selenization from Cu-In-Ga metal precursors premixed Se irrespective of the stacking order during the precursor formation step.