Characterization of layer thickness and interdiffusion in CdTe/CdS/ZTO/CTO solar cells

Accurate control of layer thickness and interdiffusion is key to process optimization in the fabrication of CdTe/CdS solar cells. This type of control requires a rapid, noninvasive characterization technique capable of accurately measuring the layer thicknesses and diffusion profiles in these multilayer structures. Variable-angle spectroscopic ellipsometry (VASE) is a technique that has the potential to perform this task. In this work, the authors have made coordinated measurements of layer thickness and composition in a specially designed set of samples using VASE, Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). These measurements have demonstrated the challenges presented by CdTe/CdS/ZTO/CTO solar cells for each of the measurement techniques. Further work remains to be done to establish VASE as an accurate characterization technique for measurement of layer thickness and interdiffusion in these structures