Ellipsometric Characterization of Materials Used in Thin Film Solar Cells

In this paper we present the characterization of materials commonly used in manufacturing thin film solar cells (TFSCs) using spectroscopic ellipsometry. In recent times, photovoltaic research has witnessed a steady increase in the field of TFSCs. Thin film solar cells have a lot of advantages over their crystalline silicon (c-Si) counterparts-their low cost and ease of fabrication being the most important factors. But to have an efficiency comparable to c-Si cells, light trapping strategies need to be developed. Using novel materials or plasmonic structures can help us achieve this. Numerical simulations are required to optimize the structure of these cells. Such simulations need the optical properties of the constituent materials as input. So it is essential to determine the optical constants of these materials accurately so that the performance of the device can be modeled appropriately. Spectroscopic ellipsometry is arguably one of the best techniques to characterize thin films today. We have measured thin films of Cr, Ag, Al-doped ZnO and amorphous silicon (a-Si). The optical constants were determined from the experimental data using regression analysis. The values agree well with reference data.