A Series of Ca(II) or Ba(II) Inorganic–Organic Hybrid Frameworks Based on Aromatic Polycarboxylate Ligands with the Inorganic M–O–M (M = Ca, Ba) Connectivity from 1D to 3D

Solvothermal reactions of Ca­(NO₃)₂ or Ba­(NO₃)₂ with aromatic carboxylate ligands afforded four new inorganic–organic hybrid frameworks, [Ca­(PBDC)­(H₂O)₃]_<i>n</i> (<b>1</b>), [Ca­(OBDC)­(H₂O)]_<i>n</i> (<b>2</b>), [Ba₅(OBDC)₄(H₂O)₂(NO₃)₂]_<i>n</i> (<b>3</b>), and [Ba₃(BTC)₂(H₂O)₄]_<i>n</i> (<b>4</b>) (H₂PBDC = terephthalic acid, H₂OBDC = phthalic acid, H₃BTC = 1,3,5-benzenetricarboxylic acid). These compounds have been fully characterized by single crystal X-ray diffraction, powder X-ray diffraction, satisfactory elemental analysis, IR spectra, and TG analysis. X-ray analysis shows that compound <b>1</b> features a one-dimensional chain (1D) structure with the I¹O⁰ connectivity, both compound <b>2</b> and compound <b>3</b> feature a two-dimensional (2D) layer structure with the I¹O¹ connectivity, I²O⁰ connectivity, respectively, compound <b>4</b> features a three-dimensional (3D) framework with a rare I³O⁰ connectivity. Thermal stabilities and luminescent properties of compounds <b>1</b>–<b>4</b> and NLO property of compound <b>4</b> have also been investigated

Large Mid-IR Second-Order Nonlinear-Optical Effects Designed by the Supramolecular Assembly of Different Bond Types without IR Absorption

Two new different-bond-type hybrid compounds, (Hg₆P₄Cl₃)­(PbCl₃) (<b>1</b>) and (Hg₂₃P₁₂)­(ZnCl₄)₆ (<b>2</b>), with supramolecular interactions between host and guest moieties, which based on metal–pnicogen, pnicogen–pnicogen, and metal–halogen bonds were obtained by solid-state reactions. Compounds <b>1</b> and <b>2</b> show large second-harmonic-generation (SHG) activity and are transparent in the wide mid-IR region, providing an effective route for searching new IR nonlinear-optical material systems by combining two or more different bond types with no IR absorption within a single compound through supramolecular assembly. Theory predications based on first-principles calculations are also performed on the SHG properties of <b>1</b> and <b>2</b>

Large Mid-IR Second-Order Nonlinear-Optical Effects Designed by the Supramolecular Assembly of Different Bond Types without IR Absorption

Two new different-bond-type hybrid compounds, (Hg₆P₄Cl₃)­(PbCl₃) (<b>1</b>) and (Hg₂₃P₁₂)­(ZnCl₄)₆ (<b>2</b>), with supramolecular interactions between host and guest moieties, which based on metal–pnicogen, pnicogen–pnicogen, and metal–halogen bonds were obtained by solid-state reactions. Compounds <b>1</b> and <b>2</b> show large second-harmonic-generation (SHG) activity and are transparent in the wide mid-IR region, providing an effective route for searching new IR nonlinear-optical material systems by combining two or more different bond types with no IR absorption within a single compound through supramolecular assembly. Theory predications based on first-principles calculations are also performed on the SHG properties of <b>1</b> and <b>2</b>

A Highly Stable 3D Acentric Zinc Metal–Organic Framework Based on Two Symmetrical Flexible Ligands: High Second-Harmonic-Generation Efficiency and Tunable Photoluminescence

A 3D metal–organic framework (MOF), [Zn­(BPHY)­(SA)]_<i>n</i> (<b>1</b>; BPHY = 1,2-bis­(4-pyridyl)­hydrazine, H₂SA = succinic acid), which crystallizes in a noncentrosysmmetric space group (<i>Cc</i>), has been solvothermally obtained and testified to be a good nonlinear-optical material with the largest second-harmonic-generation response among the known MOFs based on sysmmetric ligands and high stability. Ultraviolet-to-visible tunable emission for <b>1</b> is observed

Design and Syntheses of Electron-Transfer Photochromic Metal–Organic Complexes Using Nonphotochromic Ligands: A Model Compound and the Roles of Its Ligands

The model compound [Zn­(HCOO)₂(4,4′-bipy)] (<b>1</b>; 4,4′-bipy = 4,4′-bipyridine) is selected in this work to demonstrate the effectiveness of our previously proposed design strategy for electron-transfer photochromic metal–organic complexes. The electron-transfer photochromic behavior of <b>1</b> has been discovered for the first time. Experimental and theoretical data illustrate that the photochromism of <b>1</b> can be attributed to the electron transfer from formato to 4,4′-bipy and the formation of a radical photoproduct. The electron transfer prefers to occur between formato and 4,4′-bipy, which are combined directly by the Zn­(II) atoms. A high-contrast (up to 8.3 times) photoluminescence switch occurs during the photochromic process. The similarity of photochromic behaviors among <b>1</b> and its analogues as well as viologen compounds has also been found. Photochromic studies of this model compound indicate that new electron-transfer photochromic metal–organic complexes can be largely designed and synthesized by the rational assembly of nonphotochromic electron-donating and electron-accepting ligands

Novel p‑Type Conductive Semiconductor Nanocrystalline Film as the Back Electrode for High-Performance Thin Film Solar Cells

Thin film solar cells, due to the low cost, high efficiency, long-term stability, and consumer applications, have been widely applied for harvesting green energy. All of these thin film solar cells generally adopt various metal thin films as the back electrode, like Mo, Au, Ni, Ag, Al, graphite, and so forth. When they contact with p-type layer, it always produces a Schottky contact with a high contact potential barrier, which greatly affects the cell performance. In this work, we report for the first time to find an appropriate p-type conductive semiconductor film, digenite Cu₉S₅ nanocrystalline film, as the back electrode for CdTe solar cells as the model device. Its low sheet resistance (16.6 Ω/sq) could compare to that of the commercial TCO films (6–30 Ω/sq), like FTO, ITO, and AZO. Different from the traditonal metal back electrode, it produces a successive gradient-doping region by the controllable Cu diffusion, which greatly reduces the contact potential barrier. Remarkably, it achieved a comparable power conversion efficiency (PCE, 11.3%) with the traditional metal back electrode (Cu/Au thin films, 11.4%) in CdTe cells and a higher PCE (13.8%) with the help of the Au assistant film. We believe it could also act as the back electrode for other thin film solar cells (α-Si, CuInS₂, CIGSe, CZTS, etc.), for their performance improvement

Syntheses, Structures, and Nonlinear Optical Properties of Two Sulfides Na₂In₂MS₆ (M = Si, Ge)

The first two new Na-containing sulfides Na₂In₂MS₆ (M = Si (<b>1</b>), Ge (<b>2</b>)) in the Na₂Q–B₂Q₃–CQ₂ (B = Ga, In; C = Si, Ge, Sn; Q = S, Se) system were prepared for the first time through conventional high-temperature solid-state reaction. They are isostructural with space group <i>Cc</i> (No. 9) in monoclinic phases and feature three-dimensional frameworks built by the _∞¹[In₂MS₆]^2– (M = Si, Ge) chains through corner-sharing InS₄ tetrahedra and MS₄ (M = Si, Ge) tetrahedra, with Na⁺ cation located in the cavities. They display moderate second harmonic generation (SHG) conversion efficiencies compared with commercial AgGaS₂, with phase-matching behavior at 1800 nm and laser-induced damage thresholds 6.9 and 4.0 times higher than that of AgGaS₂, respectively. Therefore, the output SHG intensities of <b>1</b> and <b>2</b> will be ∼4.3 and 4.0 times larger than that of AgGaS₂, when the intensity of incident laser increased to close the damage energy of <b>1</b> and <b>2</b>, indicating their potential for high-power nonlinear optical application

Thiophosphates Containing Ag⁺ and Lone-Pair Cations with Interchiral Double Helix Show Both Ionic Conductivity and Phase Transition

Quaternary metal thiophosphates containing second-order Jahn–Teller distorted d¹⁰ Ag⁺ and lone-pair cations, Ag₃Bi­(PS₄)₂ (<b>1</b>), Ag₇Sn­(PS₄)₃ (<b>2</b>), and Ag₇Pb­(PS₄)₃ (<b>3</b>), were obtained by solid-state synthesis. The structural frameworks of <b>2</b> and <b>3</b> feature an infinite 1-D interchiral double helix _∞¹(Ag₃P₂S₁₁), which is rare in inorganic compounds. Compound <b>3</b> undergoes a significant first-order structural phase transition from monoclinic to hexagonal at ∼204 °C. This can be ascribed to the significant mismatch in the expansion coefficients between Pb–S (Ag–S) and P–S bonds evaluated by bond valence theory. The three compounds are Ag⁺ ionic conductors, and Ag⁺ ion migration pathways are proposed by calculating maps of low bond valence mismatch. Moreover, the optical properties of the three compounds were studied, and electronic structure calculations were performed. The combination of second-order Jahn–Teller distorted d¹⁰ cation and lone-pair cation provides a new strategy to explore new metal thiophosphates with interesting structures and promising properties

Thiophosphates Containing Ag⁺ and Lone-Pair Cations with Interchiral Double Helix Show Both Ionic Conductivity and Phase Transition

Quaternary metal thiophosphates containing second-order Jahn–Teller distorted d¹⁰ Ag⁺ and lone-pair cations, Ag₃Bi­(PS₄)₂ (<b>1</b>), Ag₇Sn­(PS₄)₃ (<b>2</b>), and Ag₇Pb­(PS₄)₃ (<b>3</b>), were obtained by solid-state synthesis. The structural frameworks of <b>2</b> and <b>3</b> feature an infinite 1-D interchiral double helix _∞¹(Ag₃P₂S₁₁), which is rare in inorganic compounds. Compound <b>3</b> undergoes a significant first-order structural phase transition from monoclinic to hexagonal at ∼204 °C. This can be ascribed to the significant mismatch in the expansion coefficients between Pb–S (Ag–S) and P–S bonds evaluated by bond valence theory. The three compounds are Ag⁺ ionic conductors, and Ag⁺ ion migration pathways are proposed by calculating maps of low bond valence mismatch. Moreover, the optical properties of the three compounds were studied, and electronic structure calculations were performed. The combination of second-order Jahn–Teller distorted d¹⁰ cation and lone-pair cation provides a new strategy to explore new metal thiophosphates with interesting structures and promising properties

Syntheses, Structures, and Nonlinear Optical Properties of Two Sulfides Na₂In₂MS₆ (M = Si, Ge)

The first two new Na-containing sulfides Na₂In₂MS₆ (M = Si (<b>1</b>), Ge (<b>2</b>)) in the Na₂Q–B₂Q₃–CQ₂ (B = Ga, In; C = Si, Ge, Sn; Q = S, Se) system were prepared for the first time through conventional high-temperature solid-state reaction. They are isostructural with space group <i>Cc</i> (No. 9) in monoclinic phases and feature three-dimensional frameworks built by the _∞¹[In₂MS₆]^2– (M = Si, Ge) chains through corner-sharing InS₄ tetrahedra and MS₄ (M = Si, Ge) tetrahedra, with Na⁺ cation located in the cavities. They display moderate second harmonic generation (SHG) conversion efficiencies compared with commercial AgGaS₂, with phase-matching behavior at 1800 nm and laser-induced damage thresholds 6.9 and 4.0 times higher than that of AgGaS₂, respectively. Therefore, the output SHG intensities of <b>1</b> and <b>2</b> will be ∼4.3 and 4.0 times larger than that of AgGaS₂, when the intensity of incident laser increased to close the damage energy of <b>1</b> and <b>2</b>, indicating their potential for high-power nonlinear optical application