Cd1-xZnxS (0less than or equal toxless than or equal to1) thin films have been prepared by the co-evaporation of US and ZnS. When the ZnS mole ratio was less than 0.85, the crystal structure of Cd1-xZnxS films was hexagonal with the c axis aligned perpendicular to the substrate. For x>0.85, however, the Cd1-xZnxS films were grown with cubic zincblende structure. As the ZnS mole ratio increased, the lattice constant of Cd1-xZnxS films decreased. The optical band gap of Cd1-xZnxS films varies from 2.41 eV for US to 3.48 eV for ZnS with x. The open circuit voltage of Cd1-xZnxS/CdTe solar cells increased with x due to reducing of the electron affinity difference between Cd1-xZnxS and CdTe films, having approximately 830 mV of the maximum value at x = 0.35. (C) 2003 Elsevier Science B.V. All rights reserved.