One-dimensional excitons in inorganic-organic self-organized quantum-wire crystals [NH2C(I)=NH2]3PbI5 and [CH3SC(=NH2)NH2]3PbI5

Optical properties of lead-iodide-based one-dimensional perovskite-type crystals [NH2C(I)=NH2]3PbI5 and [CH3SC(=NH2)NH2]3PbI5 have been investigated theoretically and experimentally. The electronic and excitonic structures are studied based on group theoretical consideration and first-principle band calculation. Strong one-dimensional anisotropy of the optical absorption spectra, large Stokes shifts (∼1.0 eV) and huge exchange energies (∼70 meV) indicate that the excitons in these crystals are one-dimensional Frenkel excitons.