Temperature dependence of radiative and non-radiative decay in the luminescence of one-dimensional pyridinium lead halide hybrids.

The photoluminescence properties of organic-inorganic pyridinium lead bromide [(pyH)PbBr] and iodide [(pyH)PbI] compounds were investigated as a function of temperature. The inorganic substructure consists of face-sharing chains of PbX octahedra. Diffuse reflectance spectra of the compounds show low energy absorption features consistent with charge transfer transitions from the PbX chains to the pyridinium cations.

Polarizable Anionic Sublattices Can Screen Molecular Dipoles in Noncentrosymmetric Inorganic-Organic Hybrids.

We report the growth and photophysical characterization of two polar hybrid lead halide phases, methylenedianiline lead iodide and bromide, (MDA)PbI and (MDA)PbBr, respectively. The phases crystallize in noncentrosymmetric space group 2, which produces a highly oriented molecular dipole moment that gives rise to second harmonic generation (SHG) upon excitation at 1064 nm. While both compositions are isostructural, the size dependence of the SHG signal suggests that the bromide exhibits a stronger phase-matching response whereas the iodide exhibits a significantly weaker non-phase-matching signal.

Influence of Dimethyl Sulfoxide on the Structural Topology during Crystallization of PbI.

Hybrid metal-organic halides are an exciting class of materials that offer the opportunity to examine how fundamental aspects of chemical bonding can influence the structural topology. In this work, we describe how solvent adducts of lead halides can influence the crystallization and subsequent annealing of these hybrid phases. While the size and shape of organic molecules are known to govern the final topology of the hybrid, we show that the affinity of solvent molecules for Pb ions may also play a previously underappreciated role.

Anionic order and band gap engineering in vacancy ordered triple perovskites.

We demonstrate that the optical absorption of the vacancy-ordered triple perovskite, Cs3Bi2Br9, can be significantly red-shifted by substituting Br with I while maintaining the layered structural topology. We also present evidence that Br ions prefer to occupy the bridging halide position within the layers in order to minimize strain within the lattice that results from the incorporation of the significantly larger iodide anions into the lattice. These results not only quantify the upper limit for I content in the layered polymorph, but also establish the minimum band gap obtainable from these Bi-based phases.