Effects of the annealing temperature and CdCl₂ treatment on the photovoltaic properties of the CdS/CdTe solar cell

Effect of the annealing temperature and CdCl₂ treatment of CdTe films prepared by vacuum evaporation on structural properties of the CdTe films and photovoltaic properties of thin film CdS/CdTe solar cells were investigated. The crystal structure of as-deposited CdTe films was zincblende type with preferential orientation of the (111) plane parallel to the substrate. The preferential orientation of the (111) plane in CdTe films decreased, and the grain size of CdTe films increased with the increase of the annealing temperature and the CdCl₂ treatment. As increasing annealing temperature, the conversion efficiency of the CdS/CdTe solar cells without and with CdCl₂ was increased due to increasing grain size and improving crystalline of CdTe films. However, the efficiency of cell annealed at the temperature of higher than 500°C for cells without CdCl₂ treatment and 450°C for cells CdCl₂ treatment was reduced because of increasing reverse saturation current density and series resitance.