Microstructural properties of (In,Ga)2Se3 precursor layers for efficient CIGS thin-film solar cells

(In,Ga)2Se3 thin films were deposited on Mo-coated glass substrates by a conventional MBE system. To control the preferred orientation of Cu(In,Ga)Se2 (CIGS) layers, the deposition temperature dependence Tdepo of the (In,Ga)2Se3 layer was investigated including observations of both surface morphology and cross-sectional structure, Raman scattering and preferred orientation in the range 50–500 °C. γ-phase (In,Ga)2Se3 films exhibited (1 1 0) and (3 0 0) X-ray diffraction lines with a little or no (0 0 6) line contribution for Tdepo>300 °C. It was revealed that a (3 0 0) preferred orientation of the (In,Ga)2Se3 layer could promote a (2 2 0/2 0 4) orientation of subsequently grown CIGS films, which were obtained only at the moderate temperatures of 300–400 °C during (In,Ga)2Se3 deposition.