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

(In,Ga)(2)Se-3 thin films were deposited on Mo-coated glass substrates by a conventional MBE system. To control the preferred orientation of Cu(In,Ga)Se-2 (CIGS) layers, the deposition temperature dependence T-depo of the (In,Ga)(2)Se-3 layer was investigated including observations of both surface morphology and cross-sectional structure, Raman scattering and preferred orientation in the range 50-500 degrees C. gamma-phase (In,Ga)(2)Se-3 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 degrees C. It was revealed that a (3 0 0) preferred orientation of the (In,Ga)(2)Se-3 layer could promote a (2 2 0/2 0 4) orientation of subsequently grown GIGS films, which were obtained only at the moderate temperatures of 300-400 degrees C during (In,Ga)(2)Se-3 deposition. (C) 2008 Elsevier B.V. All rights reserved.