Rietveld analysis of CdS/CdTe thin film junctions submitted to a CdCl2 heat treatment

• CdS/CdTe solar cells were treated in the presence of CdCl2 vapor.
• Interdiffusion in CdS/CdTe junction was investigated by Rietveld analysis.
• Sulfur replaces tellurium in the CdTe layer.
• Sulfur amount increases with the temperature of the CdCl2 heat treatment.
• Introduction of sulfur led to a nanocrystalline component in CdTe layer.

In this work we investigate the effects of a CdCl2 heat treatment on the interface of CdTe/CdS heterojunction solar cells using Rietveld analysis of X-ray diffraction patterns. Although the Rietveld method is an important tool for the study of materials by X-ray diffraction, there have been few reports of its use in thin film analysis. The results showed the occurrence of interdiffusion in the CdS–CdTe boundary, with substitution of tellurium by sulfur in the CdTe lattice that resulted in a CdSxTe1 − x alloy. The sulfur content of the alloy was greater than in previous studies. This is attributed to the low oxygen concentration during processing and the strong (111) texture of the CdTe films.