Atom Probe Tomography for Nanoscale Characterization of CdTe Device Absorber Layers and Interfaces

Cadmium telluride (CdTe) solar cells are a leading thin film technology with relatively high efficiencies. However, even the highest published efficiency CdTe cell is well below the theoretical achievable efficiency. Atomic scale characterization would provide important feedback on optimization of CdTe cells for further efficiency improvements. Atom probe tomography (APT), with both high spatial resolution and ppm composition sensitivity, is a technique well-suited for providing these details. It is demonstrated here that the compositions measured for CdTe and ZnTe by APT are sensitive to the analysis conditions, in particular the incident laser energy. Experiments demonstrating the relationships of the analysis parameters are presented. Using optimized values, APT analyses of the absorber layer and interfaces in CdTe devices were performed.