The Investigation of Donor and Acceptor States in the Nanoparticles of PbI2 Layered Semiconductor

Abstract

AbstractThe nanoparticles of PbI2 layered semiconductor, embedded in Sio2 films, were prepared by the sol-gel method. The low-temperature luminescence of PbI2 nanoparticles consists of a series of exciton lines in the region of ∼2.5eV and additional donor-acceptor recombination luminescent bands at lower energies, centered at 2.44eV (Green) and 2.07 eV (red), respectively. This paper reports the investigation of the nonexcitonic transitions, associated with of the Green and Red bands. The correlation between donor-acceptor recombination emission processes and lattice imperfections was examine, utilizing optically detected magnetic resonance (ODMR) spectroscopy. The results identified the following imperfection sites of both the Green and Red bands: an acceptor site associates with an isotropie Lead vacancy defect, [V]Pb2+ and a donor site, associate with an anisotropie Iodine vacancy, [V°]jodine. However, the results pointed on differences in relaxation processes of these bands. The relaxation processes correspond to the existence of competitive nonradiative recombination, spin-lattice relaxation and thermalization among the spin substrates. 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.