Selenium diffusion during CdCl2 treatment of CdSeTe solar cells

Selenium alloying of the absorber is a key component in achieving high efficiency polycrystalline CdSeTe solar cells. Much work has been carried out in characterizing the macroscopic electrical, optical, and structural properties of this material system. However, the movement of Se in the absorber layer and the role of CdCl2 in this process are still not fully understood. In this study, nano-scale correlative X-ray microscopy has been utilized to study ex-situ and in-situ Se-alloyed CdTe samples before, during and after CdCl2 treatment. Changes in the Se distribution were mapped by nano x-ray fluorescence and detailed information about the Se local environment in the absorber layer was collected through x-ray absorption spectroscopy ex-situ and in-situ during CdCl2 treatment. Complementary nano-Xray diffraction grain maps were collected to properly assess the evolution of stress/strain through the recrystallization process.