Characterization of Silicon Solar Cells and Module Materials Using Terahertz Radiation

In this paper, we present our investigations of silicon solar cells and module structures by means of terahertz (THz) imaging and Fourier Transform Infrared (FTIR) spectroscopy. Several types of structures were investigated: anisotropically etched surfaces of monocrystalline silicon wafers, complete commercial solar cells, interconnections of the cells, encapsulation materials, such as polydimethylsiloxane (PDMS) and glass. We demonstrated, how etching time and depth variations of the pyramid-shaped texture influence far-IR local reflectance spectra of the samples; how phase-sensitive imaging and time-domain data can be processed for full 3D characterization of cell and module structures, including layer thicknesses; positions of the surfaces and defects. In addition, applicability of sub-THz radiation to the investigation of module structures including glass is discussed.