DEFECT ENERGY-LEVEL STRUCTURE OF PBI2 SINGLE CRYSTALS

The photoluminescence spectrum of gel-grown PbI2 single crystals reveals features at 2.41, 2.31, 2.16, 2.13, 2.10, 1.99, 1.97, 1.94, and 1.85 eV, and the photoconductive response spectrum at 3.06, 2.41, 2.16, and 1.99 eV. An analysis of temperature quenching of the photocurrent indicates sensitizing centers located ∼0.46 eV above the top of the valence band. A defect energy-level structure for PbI2 has been proposed on the basis of this information. The results also suggest the existence of ∼0.03-eV optical phonons, associated with the 2.16- and 1.99-eV emission peaks. © 1968 The American Physical Society.