The Effect of Cadmium Chloride Treatment on Close-Spaced Sublimated Cadmium Telluride Thin-Film Solar Cells

The aim of this investigation is to apply advanced microstructural characterization techniques to study the effect of cadmium chloride treatment on the physical properties of cadmium telluride (CdTe) solar cells deposited via close-spaced sublimation and relate these to cell performance. A range of techniques have been used to observe the microstructural changes as well as the chemical changes before and after the cadmium chloride treatment. Electrical measurements that link the device performance with the microstructural properties of the cells have also been undertaken. Transmission electron microscopy (TEM) has revealed high densities of stacking faults in the as-grown CdTe samples. Further, it has been observed that these stacking faults are removed during the cadmium chloride treatment. These observations show that the presence of chlorine plays an important role in the removal of these defects and the subsequent production of high efficiency thin-film CdTe solar cells. Elemental analysis in the TEM indicates chlorine-rich regions appearing at the CdTe/CdS interface as well as at grain boundaries after the treatment.