Giant optical band edge shifts in hydrazine-intercalated PbI2and BiI3

Abstract
Room-temperature optical transmission measurements in the photon energy range 0.5-6 eV have been made on evaporated thin films of the semiconducting layered structures PbI2 and BiI3 during intercalation with hydrazine (N2H4). After intercalation, the optical absorption edge shifts to higher energies by approximately 1 eV for PbI2, while for BiI3 the shift is greater than 3 eV. The process is reversible. Unlike the case of the semiconducting transition-metal dichalcogenides, intercalation does not appear to introduce free carriers to the host lattice.