Revisiting a (001)-oriented layered lead chloride templated by 1,2,4-triazolium: structural phase transitions, lattice dynamics and broadband photoluminescence.

This study revisits a (001)-oriented layered lead chloride templated by 1,2,4-triazolium, TzPbCl, which recently has been an object of intense research but still suffers from gaps in characterization. Indeed, the divergent reports on the crystal structures of TzPbCl at various temperatures, devoid of independent verification of chiral phases through second harmonic generation (SHG), have led to an unresolved debate regarding the existence of a low-temperature phase transition (PT) and the noncentrosymmetric nature of the low-temperature phase. Now, by combining differential scanning calorimetry, single-crystal X-ray diffraction, dielectric, as well as linear and nonlinear optical spectroscopies on TzPbCl, we reveal a sequence of reversible PTs at = 361 K (phase I-II), = 339 K (phase II-III), and = 280 K (phase III-IV).

Luminescence and Dielectric Switchable Properties of a 1D (1,1,1-Trimethylhydrazinium)PbI Hybrid Perovskitoid.

The synthesis and investigation of the physicochemical properties of a novel one-dimensional (1D) hybrid organic-inorganic perovskitoid templated by the 1,1,1-trimethylhydrazinium (MeHy) cation are reported. (MeHy)[PbI] crystallizes in the hexagonal 6/ symmetry and undergoes two phase transitions (PTs) during heating (cooling) at 322 (320) and 207 (202) K. X-ray diffraction data and temperature-dependent vibrational studies show that the second-order PT to the high-temperature hexagonal 6/ phase is associated with a weak change in entropy and is related to weak structural changes and different confinement of cations in the available space.

[Methylhydrazinium]PbCl, a Two-Dimensional Perovskite with Polar and Modulated Phases.

Two-dimensional (2D) lead halide perovskites are a family of materials at the heart of solar cell, light-emitting diode, and photodetector technologies. This perspective leads to a number of synthetic efforts toward materials of this class, including those with prescribed polar architectures. The methylhydrazinium (MHy) cation was recently presumed to have an unusual capacity to generate non-centrosymmetric perovskite phases, despite its intrinsically nonchiral structure.