Impact of organic-inorganic wavefunction delocalization on the electronic and optical properties of one-dimensional hybrid perovskites

Low-dimensional hybrid organic-inorganic perovskites have attracted a great deal of interest thanks to their high compositional and structural flexibilities that induce distinctive optoelectronic properties, for instance for light-emitting and photovoltaic applications. Here, we study at the density functional theory (DFT) level the electronic and optical properties of two one-dimensional hybrid perovskites incorporating cyanine or Victoria blue B (VBB) dye cations. Our electronic-structure analyses indicate that in both cases the highest occupied molecular orbitals of the cation dyes are nearly aligned with the band edges of the inorganic component; however, wavefunction delocalization between the two components only arises in the cyanine-perovskite system where electronic couplings can be identified, albeit weakly, between the organic dye cations and the inorganic framework. The excited-state properties of the cyanine-perovskite system were further evaluated by carrying out time-dependent DFT calculations on representative finite cluster models based on the bulk structures. The electronic couplings between the organic and inorganic components result in a small degree of charge-transfer contributions to the low-lying excited states, which in turn leads to a broadening of the lowest absorption band.