Raman and photoluminescence studies on intercalated lead iodide with pyridine and iodine

Intercalated PbI 2 compounds were prepared by exposing crystalline films and crystalline powders of lead iodide to pyridine or iodine vapor at room temperature. Correlated studies of optical absorption, Raman scattering and low temperature photoluminescence (PL) reveal different properties in comparison with those of pure crystalline PbI 2 powder. Depending of the nature of intercalated molecules (organic or inorganic) the basic semiconducting properties of PbI 2 are dramatically modified. The main signature of iodine intercalated PbI 2 consists in a luminescence band peaking at 2.24 eV appearing at 77 K under 350 nm excitation light. In the case of pyridine intercalated PbI 2 a new intense band at about 3.3 eV in the absorption spectrum is observed. The the PL spectra of pyridine intercalated PbI 2 at 77 K change substantially when the excitation wavelength. The Raman spectra confirm the presence of pyridine between the PbI 2 layers.