Defect Energy-Level Structure of PbI2Single Crystals

The photoluminescence spectrum of gel-grown P${\mathrm{bI}}_2$ 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 P${\mathrm{bI}}_2$ 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.