Effects of transition metals incorporated into perovskite crystals on the electronic structures and magnetic...

Additive effects of transition metals (M = Cr²⁺, Co²⁺, Cu²⁺ and Y³⁺) on the electronic structures and magnetic properties of formamidinium lead halide perovskite compounds (FAPbI₃, where FA = NH₂CHNH₂⁺) were investigated by first-principle calculation using density functional theory. In the case of Cr²⁺, Cu²⁺ and Y³⁺-incorporated FAPbI₃ perovskite crystals, the electron density distribution of d-p hybrid orbital on the transition metal and iodine halogen-atoms were delocalized at frontier orbital. The total and partial density of state appeared the 3d-p hybrid orbital near the frontier orbital with narrowing band gap, yielding the wide broad absorption in the near-infrared region. The electronic correlation worked in between the localized spin on 3d orbital of the metal, and the itinerant carriers on the 5p orbital of the iodine halogen ligand and the 6p orbital of the lead atom in the perovskite crystal. The vibration behavior of the Raman and Infrared spectra were associated with change of polarization and slight distortion near the coordination structure. The considerable splitting of chemical shift of ¹²⁷I-NMR and ²⁰⁷Pb-NMR in the Co²⁺ and Cu²⁺-incorporated FAPbI₃ crystals were caused by crystal field splitting as Jahn-Teller effect with nearest-neighbor nuclear quadrupole interaction based on the charge distribution.