In situ investigation of the formation of Cu(In, Ga)Se2 from selenised metallic precursors by X-ray diffraction: The impact of Gallium, sodium and selenium excess

Abstract The chemical reactions during rapid thermal processing of stacked elemental layers were investigated by angle-dispersive in situ X-ray diffraction. With a time resolution of 5 diffractograms per minute four different solid state reactions resulting in ternary chalcopyrites were identified: (A) CuSe+InSe→CuInSe 2 , (B) Cu 2 Se+2InSe+Se→2CuInSe 2 , (C) Cu 2 Se+In2Se 3 →2CuInSe 2 , (D) Cu 2 Se+Ga2Se 3 →2CuGaSe 2 . All these reactions form pure tenary chalcopyrites. The reaction resulting in the mixed crystal Cu(In,Ga)Se 2 starts not before (B) has begun. The reaction speed of (A) and the fraction of CuInSe 2 formed by (B) depend on Na-doping and Se-pressure, (C) takes place only, if the reaction paths (A) and (B) are suppressed. Reaction (D) is observed only, if 25% In is replaced by Ga in the precursor. The diffractograms were evaluated by Rietveld refinement to give the phase contents of the samples as a function of reaction time.