Amorphous Silicon Compound Films for Surface Passivation and Antireflection Coating of Crystalline Silicon Solar Cells

This chapter gives an overview of the theoretical bases of surface passivation and antireflection coating and describes the methods and equipment used to characterize the layers created in this work. While surface passivation is quantified by the effective surface recombination velocity Seff , this parameter cannot be measured directly. Instead, the lifetime measurements by QSSPC and ”PCD carried out for this work give the effective minority carrier lifetime τeff . With certain simplifying assumptions, an upper limit for Seff can be calculated solely from τeff and the sample thickness. As shown in chapter 2.2.1, the error resulting from this simplified approach often found in literature is not negligible for good surface passivation layers, but acceptable in practice as the focus is on comparing different passivation layers. While the ”PCD was applied to obtain spatially resolved lifetime maps of the entire sample, the QSSPC was subsequently used to determine absolute values of the best areas that can be compared with the literature, as QSSPC is the established standard in c-Si photovoltaics. The refractive index and thickness of the investigated dielectric films were measured by spectroscopic ellipsometry, and the chemical composition was analyzed by Fourier-Transformed Infrared Spectroscopy (FTIR) to investigate relations with the surface passivation and optical properties.