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)PbBr3] and iodide [(pyH)PbI3] compounds were investigated as a function of temperature. The inorganic substructure consists of face-sharing chains of PbX6 octahedra. Diffuse reflectance spectra of the compounds show low energy absorption features consistent with charge transfer transitions from the PbX3 chains to the pyridinium cations. Both compounds display extremely weak luminescence at room temperature that becomes strongly enhanced upon cooling to 77 K. Broad, featureless low energy emission (λem > 600 nm) in both compounds have large Stokes shifts [1.1 eV for (pyH)PbBr3 and 0.46 eV for (pyH)PbI3] and are assigned to transitions from self-trapped excitons on the inorganic chains whereas emission at higher energy in (pyH)PbBr3 (λem = 450 nm) is assigned to luminescence from a free exciton state. Analysis of data from temperature-dependent luminescence intensity measurements gives activation energies (Ea) for non-radiative decay of the self-trapped excitons in (pyH)PbBr3 and (pyH)PbI3, (Ea = 0.077 eV and 0.103 eV, respectively) and for the free exciton in (pyH)PbBr3 (Ea = 0.010 eV). Analysis of temperature dependent luminescence lifetime data indicates another non-radiative decay process in (pyH)PbI3 at higher temperatures (Ea = 0.17 eV). A large increase in the luminescence lifetime of (pyH)PbI3 below 80 K is consistent with thermalization between triplet sublevels. Analysis of the luminescence power dependence for (pyH)PbI3 shows superlinear response suggestive of quenching by static traps.

Two chiral haloplumbate hybrids with thermochromism luminescence and application potential as luminescent thermometers

Two noncentrosymmetric haloplumbate hybrids, [C6H10(NH3)2][PbCl4] (1) and [C6H10(NH3)2][PbBr4] (2), have been synthesized. Crystals of 1 and 2 belong to the chiral space group P212121. The inorganic parts comprise a one-dimensional chain structure for 1 and a two-dimensional sheet structure for 2. Both compounds exhibit thermochromic luminescence originating from dual emission and have potential applications as self-referencing luminescent thermometers.

Molecular Engineering of Pure 2D Lead-Iodide Perovskite Solar Absorbers Displaying Reduced Band Gaps and Dielectric Confinement

Pure 2D lead-iodide perovskites typically demonstrate poor charge transport and compromised visible light absorption, relative to their 3D congeners. This hinders their potential use as solar absorbers. Herein, the systematic tuning of pyridinium-based templating cations is reported to introduce intermolecular interactions that provide access to a series of new 2D lead-iodide perovskites with reduced inter-octahedral distortions (largest Pb-(μ-I)-Pb bond angles of 170-179°) and very short inorganic interlayer separations (shortest I⋅⋅⋅I contacts ≤4.278-4.447 Å). These features manifest in reduced band gaps (2.35-2.46 eV) and relaxed dielectric confinement (excitonic binding energies of 130-200 meV). As a consequence, they demonstrate (more than ten-fold) improved photo- and electrical conductivities relative to conventional 2D lead-iodide perovskites, such as that templated by 2-(1-naphthyl)ethylammonium. Through computational studies, the origin of this behavior was shown to derive from a combination of short iodoplumbate layer separations and the aromaticity of the organic dications.

Hybrid iodoplumbates with metal complexes: syntheses, crystal structures, band gaps and photoelectric properties

With the in situ-generated [Pb(MCP)₄]²⁺ (HMCP⁺ = 1-methyl-4-(carboxyl)pyridinium) or [M(phen)₃]²⁺ (M = Co, Fe and Ni; phen = 1,10-phenanthroline) complexes as structural directing agents and charge-balancing ions, we solvothermally synthesized and structurally characterized four new organic-inorganic hybrid iodoplumbates. Compound K₂[Pb(MCP)₄]Pb₃I₁₀ (1) represents the first K⁺ and [Pb(MCP)₄]²⁺ co-templated hybrid haloplumbate, and exhibits a curve-like anionic layer of [Pb₃I₁₀]_n^4n-. Compounds [M(phen)₃]Pb₂I₆·CH₃CN (M = Co (2), Fe (3) and Ni (4)) have isostructural phases, and feature a one-dimensional (1D) [Pb₂I₆]_n^2n- anionic chain characteristic of pyramid-like [PbI₅] units. The optical property studies show that compounds 1-4 exhibit semiconductor behaviors with the band gaps of 1.98-2.68 eV. In addition, the title compounds exhibited interesting photoelectrical responsive properties, with the photocurrent density in the order of 1 > 3 > 2 > 4. The thermal stabilities of the title compounds 1-4, as well as the theoretical band structure and density of states (DOS) of compounds 1 and 2 have also been studied.

Semiconductive donor promoted photochromism of iodoplumbate hybrids

The entirely different photochromic behaviors of two iodoplumbate hybrids indicate the driving role of excitation of the PbI₃⁻ chain donor and the negative role of charge transfer in photoinduced electron transfer and photochromism.

The crystal structure of 3-butyl-1-methyl-1H-imidazol-3-ium catena-poly[tris(μ2-bromido-κ 2 Br:Br)lead(II)], C8H15Br3N2Pb

C8H15Br3N2Pb, orthorhombic, P212121 (no. 19), a = 7.7781(9) Å, b = 9.7129(15) Å, c = 19.158(2) Å, V = 1447.3(3) Å3, Z = 4, R gt(F) = 0.0376, wR ref(F 2) = 0.0780, T = 100 K.

Organic cation directed hybrid lead halides of zero-dimensional to two-dimensional structures with tunable photoluminescence properties

A series of new inorganic–organic hybrid lead halides have been solvothermally synthesized and characterized with tunable luminescence properties from yellow, orange to red emissions with the largest reported Stokes shift.

Do alkyl groups on aromatic or aliphatic structure directing agents affect water stabilities and properties of hybrid iodoargentates?

Two types of in situ formed structure directing agents (SDAs) including aromatic triphenylphosphine (PPh₃)- and aliphatic piperazine (H₂pp)-derivative cations were used to synthesize five new hybrid iodoargentates, namely (EtPPh₃)Ag₃I₄ (1, Et = ethyl), (n-PrPPh₃)Ag₃I₄ (2, n-Pr = n-propyl), (i-PrPPh₃)Ag₅I₆ (3, i-Pr = isopropyl), (Me₄pp)_0.5AgI₂ (4, Me = methyl), and (H₃app)₂(Ag₂I₆)·2I·2H₂O (5, app = N-aminoethylpiperazine). A comparative study of the two types of SDAs on the structures, stabilities and properties of hybrid iodoargentates was performed in detail. Structurally, except for (EtPPh₃)⁺ and (n-PrPPh₃)⁺, which both directly form (Ag₃I₄)^- anionic chains in 1 and 2, three SDAs generate hybrid iodoargentates different from each other with inorganic anions ranging from a 0-D (Ag₂I₆)^4- dimer to 1-D α-type (AgI₂)^- and (Ag₅I₆)^- chains. With regard to the electronic structures, aromatic PPh₃-derivative cations make noticeable contributions to the bottom of the conduction bands, while aliphatic pp-derivative cations make nearly no contribution to the frontier orbitals, clearly indicating their different ways to adjust the band gaps. With regard to stability, the decomposition temperatures of 1-3 in the range of 324-349 °C are noticeably higher than the values of 217 and 225 °C for 4 and 5. Furthermore, 1-4 exhibit good water stabilities, which is ascribed to the alkylation reactions precluding the formation of strong hydrogen bonds between alkylated SDAs and extraneous H₂O molecules. Contrarily, the presence of typical hydrophilic [double bond, length as m-dash]NH₂⁺, [triple bond, length as m-dash]NH⁺ and -NH₃⁺ groups on the protonated (H₃app)³⁺ cation makes 5 sensitive to water and a hydrolysis reaction occurs to generate a cubic AgI phase. Finally, 1-3 exhibit high photocatalytic efficiencies for the degradation of rhodamine B (RhB) dye in wastewater under visible light. All conclusions obtained here will help a lot in the synthesis of stable functional metal halide-based hybrids.

Assembly of donor–acceptor hybrid heterostructures based on iodoplumbates and viologen coordination polymers

Two D–A hybrid heterostructures have been formed by the insertion of electron-rich iodoplumbates into viologen coordination polymers, which exhibit highly effcient photocatalytic degradation RhB under visible light irradiation.

An inorganic–organic hybrid crystal with a two-step dielectric response and thermochromic luminescence

An iodoplumbate-based hybrid crystal [C₂-Apy][PbI₃] (1) (C₂-Apy⁺ = 1-ethyl-4-aminopyridinium) was synthesized and characterized structurally.

A multi-functional iodoplumbate-based hybrid crystal: 1-propyl-4-aminopyridinium triiodoplumbate

The temperature-dependent photoluminescence, dielectric and impedance spectra, as well as crystal structures have been investigated for the iodoplumbate-based hybrid crystal, [C₃-Apy][PbI₃] (1) (C₃-Apy⁺ = 1-propyl-4-aminopyridinium).

Relaxor-like and switchable dielectric behavior in a rare noncentrosymmetric 3D iodoargentate hybrid

A rare noncentrosymmetric three-dimensional (3D) iodoargentate hybrid, namely, [Cd(en)₃]Ag₂I₄ (1), was prepared using a simple solution process.

Transition metal complex directed lead bromides with tunable structures and visible light driven photocatalytic properties

Six new compounds were synthesized and characterized as [Co(2,2-bipy)₃]₂{[Co(2,2-bipy)]₃Pb₇Br₂₄} (1), [Co(2,2-bipy)₂Br]PbBr₃(2), [TM(phen)₃]Pb₂Br₆(TM = Co (3) and Ni (4)), [Co(2,2-bipy)₃]Pb₃Br₉(5) and [Co(2,2-bipy)₃]Pb₅Br₁₃·CH₃CN (6).

Investigation of thermochromic photoluminescent, dielectric and crystal structural properties for an inorganic–organic hybrid solid of [1-hexyl-3-methylimidazolium][PbBr3]

An imidazolium-based bromoplumbate hybrid solid shows fascinating luminescence thermochromism, appealing dielectric anomaly and relaxation.