Electronic Structures, Spectroscopic Properties, and Thermodynamic Characterization of Alkali Metal and Transition Metal Incorporated Perovskite Crystals by First-Principles Calculation

Abstract

Influence of alkali metals (Na, K) or transition metals (Co, Cr, Cu, and Y) incorporated into perovskite crystal on the electronic structures, spectroscopic and magnetic properties, and thermodynamic properties was investigated by first-principles calculation. Incorporation of Na or K into the perovskite crystal generated 3s, 3p, 4s, and 4p orbitals of Na or K above the conduction band, which promoted the charge transfer from alkali metal to the conduction band, accelerating the electron diffusion related to the photovoltaic properties. For the Cr, Cu and Y-incorporated perovskite crystals, the electron density distribution of d-p hybrid orbital on the transition metal and iodine halogen ligand were delocalized at frontier orbital. 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 127 I-NMR and 207 Pb-NMR in magnetic field were caused by crystal field splitting as Jahn-Teller effect with nearest-neighbor nuclear quadrupole interaction based on the charge distribution. Decrease of the Gibbs free energy and entropy indicated the thermodynamic stabilization without scattering carrier diffusion as phonon effectiveness. The decrease of the entropy was based on a slight change of stretching vibration mode of Pb-I bond with vending mode of N-H and C-H bonds in the infrared and Raman spectra. The minor addition of alkali metal or transition metal into the perovskite crystal would improve the photovoltaic properties, open voltage related to band gap, and short-circuit current density based on the carrier diffusion with phonon effectiveness.