Chapter 5 - Optical Properties of I–III–VI 2 Compounds

Abstract

Publisher Summary The chapter discusses the band structure, band gaps, absorption, transmission, and reflections of I–III–VI2 compounds, such as CuInS2, CuInSe2, CuGaSe2, and their solid solutions. The low temperature photoluminescence studies on the compounds extensively discuss the transitions of defect levels that take place. On the other hand, the kinds of defect levels that encourages enhancing the efficiency of the cells and discourages to slip the efficiency of the cells are discussed. The Raman spectroscopy analysis significantly details structure of the compounds, secondary phases and supports the X-ray diffraction (XRD) analysis to confirm the same. The chapter discusses the band structure of I–III–VI2 compounds and mentions that electrolyte electroreflectance (EER) investigations on CuInS2 single crystals showed that room temperature energy gaps corresponding to these transitions are equal. There are several models to determine the absorption coefficient (α) of the absorbing thin films on the nonabsorbing substrates. The CuInS2 is an excellent ideal absorber for thin film solar cells owing to its suitable band gap of 1.53 eV matching with solar spectrum. The photoluminescence is virtually an optical process tool to assess the quality of the material, as well as to determine probable defect states. The chapter discusses about the defect states in the solar cell absorbers, such as CuInSe2, CuGaSe2, CuInS2, and their possible solid solutions Cu(In1–xGax)Se2, CuIn(Se1–xSx)2, and solar cells. The Raman spectroscopy (RS) is one of themarvelous tools to determine single or polytype structures and secondary phases of the materials.