Chemical and mechanical techniques enabling direct characterization of the CdS/CdTe heterojunction region in completed devices

The composition and structure of the CdS/CdTe heterojunction is critical to device performance. However, it is difficult to access this region in devices employing the conventional superstrate configuration. In this work, we report on the development of two techniques for exposing the CdS window layer in completed CdTe solar cells. First, we report on a chemical etch that selectively removes CdTe and exposes the CdS back surface. In addition, we demonstrate a thermo-mechanical lift-off technique that allows clean separation at the TCO/CdS interface. These techniques enable simple, quick sample preparation for characterization of the heterojunction region of completed devices.