Chemical structure of buried interfaces in CdTe thin film solar cells

We have used a lift-off technique and X-ray photoelectron spectroscopy to probe initially buried interfaces of a CdTe solar cell after CdCl₂ and contact treatments. We find that the cleavage takes place at or near the CdTe/CdS interface. On both surfaces, Cl is present, most likely due to diffusion through the CdTe layer during the high-temperature CdCl₂ activation step. Te is present on both cleavage-exposed surfaces, as well as on the external back contact surface before cleavage. We find that the Te atoms are in (at least) two different chemical environments. From our data we are able to paint a comprehensive picture of the chemical structure of the CdTe/CdS interface.