Halogen Effect on the Photoluminescence of 1D Hybrid Lead Halide Perovskites with a Bipyridinium Cation

Abstract

Organic−inorganic hybrid perovskites (OIHPs) have emerged as a prominent class of materials due to their diverse structures and tremendous potential in optics and electronics. Herein, we present two one-dimensional (1D) OIHPs, (C 22 H 18 N 2 )(PbX 3 ) 2 (X = Cl or Br), in the form of single crystals and microcrystals that incorporate a bisprotonated bipyridinium compound as the organic cationic component. These two OIHPs possess a double-perovskite 1D chain structure, where the organic bipyridinium cations are linked to the perovskite octahedra through N−H•••X hydrogen bonds. The chloride OIHP displays two emission bands that are attributed to the singlet free exciton of the organic moiety and the singlet self-trapped exciton (STE) of the perovskites, respectively. In contrast, the bromide analogue exhibits a single broad emission band originating from the triplet STE of the perovskites. Excitation wavelength and temperature-dependent photoluminescence studies provide insights into the distinct emission mechanisms of these two Pb-based OIHP materials.