The investigation of donor and acceptor states in nanoparticles of the layered semiconductor PbI2

The low-temperature luminescence of PbI2 nanoparticles consists of exciton lines in the region of ∼2.49 eV and additional donor-acceptor recombination luminescent bands at lower energies, centered at 2.44 (green) and 2.07 eV (red). The correlation between donor-acceptor recombination emission processes and lattice imperfections was examined, utilizing optically detected magnetic resonance spectroscopy. The results identified the following imperfection sites in both the green and red bands: an acceptor site, associated with an isotropic lead vacancy defect, [V−]Pb2+ and a donor site, associated with an anisotropic iodine vacancy, [V0]iodine. Thus, the results suggest that the red band corresponds to stoichiometric defects at the surface, while the green band corresponds to the same stoichiometric defects at the interior part of the nanoparticles.