Phase Transition, Dielectrics, Single-Ion Conductance, and Thermochromic Luminescence of a Inorganic–Organic Hybrid of [Triethylpropylammonium][PbI3]

[Methylhydrazinium]2PbCl4, 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. Here, we witness this effect once again in the case of the Ruddlesden–Popper perovskite phase of formula MHy₂PbCl₄. MHy₂PbCl₄ features three temperature-dependent crystal phases, with two first-order phase transitions at T₁ = 338.2 K (331.8 K) and T₂ = 224.0 K (205.2 K) observed in the heating (cooling) modes, respectively. Observed transitions involve a transformation from high-temperature orthorhombic phase I, with the centrosymmetric space group Pmmn, through the room-temperature modulated phase II, with the average structure being isostructural to I, to the low-temperature monoclinic phase III, with non-centrosymmetric space group P2₁. The intermediate phase II is a rare example of a modulated structure in 2D perovskites, with Pmmn(00γ)s00 superspace symmetry and modulation vector q ≅ 0.25c*. MHy₂PbCl₄ beats the previous record of MHy₂PbBr₄ in terms of the shortest inorganic interlayer distance in 2D perovskites (8.79 Å at 350 K vs 8.66 Å at 295 K, respectively). The characteristics of phase transitions are explored with differential scanning calorimetry, dielectric, and Raman spectroscopies. The non-centrosymmetry of phase III is confirmed with second harmonic generation (SHG) measurements, and polarity is demonstrated by the pyroelectric effect. MHy₂PbCl₄ also exhibits thermochromism, with the photoluminescence (PL) color changing from purplish-blue at 80 K to bluish-green at 230 K. The demonstration of polar characteristics for one more member of the methylhydrazinium perovskites settles a debate about whether this approach can present value for the crystal engineering of acentric solids similar to that which was recently adopted by a so-called fluorine substitution effect.

The properties of an unknown halide analogue of extant two-dimensional methylhydrazinium perovskites of formula MHy₂PbCl₄ were explored. A multitechnique investigation of the structural, polar, dielectric, nonlinear, and linear optical properties of all crystal phases of MHy₂PbCl₄ forms the basis of the present contribution.

Tunable thermotropic phase transition triggering large dielectric response and superionic conduction in lead halide perovskites

Lead halide perovskites show tunable structural phase transition, accompanied by large dielectric response and superionic conduction.

A novel 3-D lead-iodide polymer based on the linkage of rare binuclear [Pb2I]3+ cations and anionic bis(pyrazinyl)-trizole bridges

A novel 3-D lead-iodide polymer [Pb₂I(μ-bpt-z)₃]_n (1, Hbpt-z = 3,5-bis(pyrazinyl)-1,2,4-trizole) has been hydrothermally prepared and structurally characterized. 1 offers the first example of a 3-D lead-iodide polymer built up from the linkage of rare binuclear [Pb₂I]³⁺ cations and anionic bis(pyrazinyl)-trizole bridges. 1 exhibits photoluminescent and photocurrent response properties, and its density functional theory calculation was also studied.

PbX2(OOCMMIm) (X = Cl, Br): photoluminescent organic-inorganic hybrid lead halide compounds with high proton conductivity

Differences in the electronegativity and hydrophilicity of halogens lead to differences in proton-conducting and photoluminescence properties in hybrid organic-inorganic lead halide compounds of [PbX₂(OOCMMIm)]_n (X = Cl (1), Br (2), HOOCMMIm = 1-carboxymethyl-3-methylimidazolium).

Ultrahigh phase transition temperature in a metal–halide perovskite-type material containing unprecedented hydrogen bonding interactions

An ABX₃ perovskite-type compound (N,N-dimethylethanolammonium)CdCl₃ with hydrogen bonding interactions between organic ammonium cations undergoes a phase transition at super-high temperatures.

Extra thermo- and water-stable one-dimensional organic-inorganic hybrid perovskite [N-methyldabconium]PbI3 showing switchable dielectric behaviour, conductivity and bright yellow-green emission

Haloplumbate-based perovskites display promising functionalities for advanced photovoltaic, optoelectronic and other applications with high performances and low costs. Herein, we present a study of variable-temperature crystal structures, dielectrics and conductance at 153-513 K, and luminescence at ambient temperature for a one-dimensional organic-inorganic perovskite, [N-methyldabconium]PbI3 (1). Hybrid 1 shows extra thermo- and water-stability (thermal decomposition at ca. 653 K), switchable dielectric behaviour and conductance at around 348 K, owing to symmetry-breaking structure phase transition from the hexagonal space group P63/mmc in the high-temperature phase to the orthogonal space group Pcba in the low-temperature phase, and bright yellow-green emission at room temperature, originating from the electron transition within the semiconducting {PbI3}∞ chains. This study will broaden the scope of lead halide-based hybrid materials for practical application in optical and electrical devices.

Temperature-Responsive Luminescent Solar Concentrators: Tuning Energy Transfer in a Liquid Crystalline Matrix

Temperature-responsive luminescent solar concentrators (LSCs) have been fabricated in which the Förster resonance energy transfer (FRET) between a donor-acceptor pair in a liquid crystalline solvent can be tuned. At room temperatures, the perylene bisimide (PBI) acceptor is aggregated and FRET is inactive; while after heating to a temperature above the isotropic phase of the liquid crystal solvent, the acceptor PBI completely dissolves and FRET is activated. This unusual temperature control over FRET was used to design a color-tunable LSC. The device has been shown to be highly stable towards consecutive heating and cooling cycles, making it an appealing device for harvesting otherwise unused solar energy.