Abstract
Hybrid organic-inorganic metal perovskites (ABX(3), A- organic cation, B-metal ion, X-halide ion) have shown significant potential as thin-film solar cells or Dye solar cells (DSC) materials. Using a time-dependent density functional theory (TDDFT) study, this work explores the role that the central organic cation plays in defining the optoelectronic and physical properties of metal perovskites. Cubic phases of CH3NH3PbI3, CH3NH3PbCl3, CH3NH3PbICl2, and CH3NH3PbI2Cl perovskite structures are investigated using TDDFT with Gaussian 16. Electronic and optical properties, including transition energy, band gap, IR and absorption spectra and vibrational frequencies are examined. It is observed that the organic cation reduces the unit cell volume of the outer metal halide structure from approximately 9-20% for different perovskite materials. The peak optical absorption also correspondingly decreases by a significant margin, ranging from about 40-60%.