CdS barrier to minimize Zn loss during CdCl2 treatment of Cd-Zn-Te absorbers.

Highlights • The devices fabricated after the CdCl 2 treatment exhibited a diode-like behavior. • CdS cap on Cd-Zn-Te acts as a barrier to prevent Zn loss during the CdCl 2 treatment. • Retained Zn in the bulk of Cd-Zn-Te with chlorine decorating the grain boundaries. • Band gap maintained after the CdCl 2 treatment on Cd-Zn-Te fitted with CdS cap. • Method can be extended to other high band gap alloys of CdTe (Cd-Mg-Te, Cd-Mn-Te). Abstract A major challenge in the fabrication of high band gap II–VI polycrystalline solar cells is to preserve the original composition of the absorber after the CdCl 2 activation treatment. In this study, a method is demonstrated to maintain the Cd-Zn-Te alloy absorber composition during its exposure to the CdCl 2 treatment. A thin film of CdS was applied as a barrier on the back surface of the high band gap polycrystalline Cd (1−x) Zn x Te (x = 20% by atomic ratio, corresponding band gap 1.72 eV) before the CdCl 2 treatment. Using transmission electron microscopy and energy dispersive spectroscopy, it was observed that the composition of Cd-Zn-Te was maintained after the CdCl 2 treatment. The devices fabricated after removing the thin film of CdS, exhibited diode-like behavior. A significant increase in the quantum efficiency near the short wavelength region was observed, and the band gap of Cd (1−x) Zn x Te was maintained. [ABSTRACT FROM AUTHOR]