Optical Properties of Bound and Localized Excitons

In the previous chapter we discussed mainly the optical properties of intrinsic free excitons. Here we consider excitons bound to various types of defects and how they are observed in optical spectra (mainly in luminescence). Excitons can also get trapped in localized states in potential fluctuations of disordered bulk materials. We will discuss how this localization affects the optical spectra and present different approaches for the modeling of localization properties. Many of these aspects are also relevant for the structures of reduced dimensionality presented in the next chapter.