CdTe thin films were prepared by thermal evaporation under a vacuum of 10 - 6 Torr and with a deposition rate of about 60nm/min. X-ray diffraction studies of the as-deposited films revealed polycrystalline films with cubic structure. The effect of heat treatment with or without CdCl 2 enhances the grain size and improves the crystallinity of the films. Moreover, the activation energy decreases upon heat treatment with or without CdCl 2 for CdTe thin films. The optical spectra of CdTe films show interference oscillations indicating the good optical quality of these films. The calculated energy gap decreases with or without CdCl 2 treatments. The current-voltage and capacitance-voltage characteristics for dark and illuminated three junction cells are measured. By analysing these measurements the different junction parameters are obtained and the effect of CdCl 2 treatment on the performance of the heterojunctions is investigated.