Single-phase Cu(In,Ga)(Se,S)(2) alloys have been prepared using a novel two-step selenization/sulfurization growth process to react copper-indium-gallium alloy films. The growth scheme differs critically from standard two-step growth processes and is based on the manipulation of the reaction kinetics in order to inhibit the formation of stable ternary phases. In the first step, the metallic precursors are reacted with H2Se/Ar to produce a composite alloy containing a mixture of binary selenides and at least one partially reacted ternary alloy. The film is then exposed to H2S/Ar at a defined temperature to produce uniform, single-phase pentenary Cu(In.Ga)(Se,S)(2) alloys. Solar cell results for Cu(In,Ga)(Se,S)(2) films with the S/(S + Se) ratio from 0.23 to 0.65 at a fixed Ga/(Ga + In) ratio are presented. (C) 2003 Elsevier B.V. All rights reserved.