The effect of substrate temperature on cadmium telluride films in high temperature vapor deposition process

TL;DR

This study investigates how substrate temperature influences the crystallization, internal stress, and structural quality of CdTe thin films prepared via high-temperature vapor deposition, relevant for improving solar cell efficiency.

Contribution

It provides new insights into the relationship between substrate temperature and film quality, internal stress, and defect formation in CdTe thin films.

Findings

Higher substrate temperatures improve crystallization quality.

Internal stress increases with substrate temperature.

Stacking faults contribute to stress generation.

Abstract

Physical vapor high-temperature deposition of CdTe thin films is one of the main methods for preparing high-efficiency CdTe solar cells, but high-temperature deposition also has an impact on the internal structure of the film. The difference in thermal expansion coefficients between the substrate and CdTe leads to the generation of internal stress in the CdTe thin film during the cooling process. In this work, we prepared thin films with different substrate temperatures using a homemade GVD device, and observed by SEM that the crystallization quality of the film gradually improved with the increase of substrate temperature, but accompanied by the shift of XRD peak position. We calculated the internal stress situation of the film by the shift amount, and the possible causes of stress generation were speculated by the results of TEM and SAED to be the combined effects of the different thermal expansion coefficients between the substrate and the film and the stacking fault defects inside the film.