SIZE QUANTIZATION OF EXCITONS IN PBI2 MICROCRYSTALLITES

PbI2 microcrystallites are embedded into E-MAA copolymer by ion exchange method. Platelet shaped microcrystallites with different thicknesses are prepared for the subsequent heat treatment procedures. In the absorption spectra of these samples, exciton structures due to size quantization appear in the visible and near ultraviolet regions. For the crystallites with more than three layers, the layer thickness dependence of the exciton energy is well explained by the exciton confinement model. For one and two layer crystallites, however, exciton energies deviate to the lower energy from the theoretical value, and its origin is discussed.