Photoluminescence (PL) provides direct information about the electronic states and carrier dynamics in a material. There are three phenomena that are observed when a sample of amorphous Chalcogenides is illuminated by bandgap light: creation of light-induced defects, photodarkening (PD), and volume expansion (VE). This chapter presents theories of PL, PD, and VE, and discusses the results in the light of experimental observations. It first derives a theory of calculating the rates of spontaneous emission within the two-level approximation, and then under nonthermal equilibrium and thermal equilibrium. The radiative lifetime is calculated from the inverse of the maximum rates obtained at the thermal equilibrium and is compared with experimental ones in hydrogenated amorphous silicon. The chapter also presents a theory of PD and photo-VE is presented. Finally, the chapter presents the theory of electroluminescence from organic semiconductors is presented, including the mechanisms of operation of organic light emitting diodes (OLEDs) and thermally activated delayed fluorescence–based OLEDs.
|Title of host publication||Optical Properties of Materials and Their Applications|
|Place of Publication||New Jersey|
|Publisher||John Wiley & Sons|
|Number of pages||37|
|Publication status||Published - 2020|