Growth and properties of the Cd1−xZnxS thin films for solar cell applications

Cd1−xZnxS (0≤x≤1) thin films have been prepared by the co-evaporation of CdS 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 CdS 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.