Advanced Light Management for CZTSe Alternative Thin Film Solar Cells

This book highlights the importance of optical characterization as a mean to reach high efficiencies in thin film solar cells. Characterization of the CZTSe cell material was performed using two approaches. Ellipsometry measurements were used to characterize thin flat layers while rough layers were characterized using a developed model. The proposed model is a mean of estimating the refractive index and the absorption coefficient of a rough material from a set of reflectance and transmission measurements. A simulation model was built based on the characterized optical parameters and was used to predict the optical behavior of the cell and optimize the whole stack optically. Optimization was focusing on minimizing the optical losses through first optimizing the thickness of each layer using the built simulation model and secondly optimizing the optical performance using Anti-Reflection Coating (ARC). Reflection values decreased from about 10% to values as low as 0.45% at the central wavelength with an average integrated reflection over the whole wavelength spectrum of interest of only 2%. These enhancements has lead to higher cell efficiencies with a certified record of 9.7 %.