Through-the-glass spectroscopic ellipsometry of superstrate solar cells and large area panels

We have advanced the technique of through-the-glass spectroscopic ellipsometry (SE) toward the nondestructive, non-invasive analysis of large area coated glass plates and completed solar modules in the superstrate configuration. The focus of this work involves reducing the effects of artifacts due to changes in the polarization state of light as it traverses the glass to the film side. By including the effects of (i) strain in the glass, (ii) differences in soda lime glass optical properties at the tin side versus the film side, and (iii) possible collection of both tin side and film side reflections, the accuracy in the determination of film properties in through-the-glass measurements can be improved. For example, measurements of the index of refraction spectra of the uncoated film side glass using a through-the-glass method agree with direct measurements from the uncoated film side to within ±0.004 over the full spectral range of through-the-glass measurements (~300 to 1600 nm).