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 T_depo 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 T_depo>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.