CuIn1-xGaxSe2 thin films were. prepared by one step electrodeposition from reagents CuSO4, In-2(SO4)(3), SeO, and Ga-2(SO4)(3). The influence of deposition parameters (electrolyte composition, concentration of reagent and deposition potential) on film composition was studied. The structure, composition, morphology, optical and electrical properties of as-deposited and of annealed films were investigated. The X-ray diffraction analysis showed that the films annealed above 350 degrees C have a chalcopyrite structure of CuInSe2. The concentration of In-2(SO4)(3) affects the composition of In and Se in the films. The optical band gap of the films was varied between 1.01 and 1.26 eV by increasing the Ga content in the films. The electrical resistivity of CIS at room temperature decreased down to 10 Omega cm. The conduction mechanism in the CIS films was investigated in the temperature range 150 to 350 K. (c) 2005 Elsevier B.V. All rights reserved.