The CBD-Zn(O,S,OH)(x) buffer process is reviewed. Applying this buffer, our highest efficiencies are achieved, such as a circuit (or submodule) efficiency of 14.2% at an aperture area of 864 cm(2) on a 30cm x 30cm-sized substrate and module efficiencies of 13.4% at an aperture area of 3459 cm(2) on a mosaic module in which four 30cm x 30cm-sized circuits are connected in parallel and 12.8% at an aperture area of 3456 cm(2) on a 30cm x 120cm-sized substrate. Our module structure is a cover glass/EVA/MOCVD-BZO window/CBD-Zn(O,S,OH)(x) buffer/CIGSS surface layer/CIGS absorber/Mo base electrode/soda-lime glass. Development of both the hardware (i.e. CBD apparatus) applicable to the mass production and the suitable control parameters is necessary to establish the robust baseline process for the CBD-Zn(O, S,OH)(x) buffer. Finding of %T monitoring and post-deposition light soaking in this buffer process contributes not only to improve the reproducibility, but also to enhance the electrical yield and the I-V performance. (C) 2004 Elsevier Ltd. All rights reserved.