8 research outputs found

    Effects of Sulfur Oxidation on the Electronic and Charge Transport Properties of Fused Oligothiophene Derivatives

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    Comparative studies of a series of oligothiophenes and their oxidized compounds are carried out by means of quantum chemical calculations. Taking aim at the effects of chemical oxidation of thienyl sulfur on the modulation of electronic structures and charge transport properties of oligothiophenes, the geometrical structures, molecular reorganization energies upon gaining or losing electrons, molecular ionization potentials (IPs) and electron affinities (EAs), molecular aromaticities, frontier molecular orbitals, and charge mobilities are analyzed in detail to determine the structure–property relationships for the investigated oligothiophenes and their corresponding oxidized counterparts. The calculated results show that the oxidation of thienyl sulfur into the corresponding <i>S</i>,<i>S</i>-dioxide could possibly change the charge transport characteristics of fused oligothiophene from hole transporting materials to bipolar or electron transporting materials, shedding light on the exploration of n-type thiophene-based semiconductors

    Counteranion-Mediated Intrinsic Healing of Poly(ionic liquid) Copolymers

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    Fabrication of self-healing/healable materials using reversible interactions that are governed by their inherent chemical features is highly desirable because it avoids the introduction of extra groups that may present negative effects on their functions. The present study exploits the inherently featured electrostatic interactions of the ion pairs in polymeric ionic liquids (PILs) as the driving force to fabricate healable PIL copolymers. The healable PIL copolymers are fabricated through the copolymerization of the IL monomers with ethyl acrylate followed by the replacement of Br<sup>–</sup> counteranions with bulkier ones such as bis­(trifluoromethanesulfonyl)­imide (TFSI<sup>–</sup>). Without modifying the chemical structures of the PIL moieties, the healing performance of the as-prepared PIL copolymers can be effectively mediated by their counteranions. The PIL copolymers that do not possess healability when paired with Br<sup>–</sup> counteranions become healable after exchanging the Br<sup>–</sup> counteranions with larger-sized ones (e.g., TFSI<sup>–</sup>). The PIL copolymers paired with bulky counteranions exhibit enhanced chain mobility and highly reversible ion-pair interactions, which facilitate the healing process. The PIL copolymers paired with TFSI<sup>–</sup> anions can completely heal the damage/cut upon heating at 55 °C for 7.5 h. Meanwhile, the counteranions with larger sizes not only benefit the healing performance of the PIL copolymers but also enhance their ion conductivity. The ion conductivity of the PIL copolymers paired with TFSI<sup>–</sup> is an order of magnitude higher than that of the PIL copolymers paired with Br<sup>–</sup>. Therefore, the as-prepared healable PIL copolymers are potentially useful as solid electrolytes in PIL-based energy devices to improve their safety and reliability

    Terminal Modulation of D−π–A Small Molecule for Organic Photovoltaic Materials: A Theoretical Molecular Design

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    A class of D−π–A–A type small-molecule donor materials used in heterojunction solar cell has been designed and investigated by means of quantum chemical calculations. A linear D−π–A molecule containing triphenylamine (TPA), ethynylbenzene (EB), and diketopyrrolopyrrole (DPP) is end-capped with various electron acceptors to further enhance its electron-accepting capability. To gain a better understanding of the effects of terminal acceptors on the modulation of electronic and optical properties of D−π–A molecule, the geometrical structures, light-absorbing capacities, frontier orbitals, exciton binding energies, intramolecular charge transfer (ICT) properties, and exciton dissociation rates at the interface are analyzed in detail to establish the structure–property relationships for D−π–A–A type materials. The calculated results indicate that the terminal modulation is an effective strategy to enhance light-absorbing capacities, ICT properties, and exciton dissociation at the heterojunction interface. The predicted power conversion efficiency (PCE) of designed molecules by Scharber diagram could reach up to more than 8%, which sheds light on the exploration of high-performance small-molecule donors for photovoltaic applications

    Electronic and Charge Transport Properties of <i>peri</i>-Xanthenoxanthene: The Effects of Heteroatoms and Phenyl Substitutions

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    The electronic and charge transport properties of <i>peri</i>-xanthenoxanthene (PXX) and its phenyl-substitued derivative (Ph-PXX) are explored via quantum chemical calculations. To gain a better understanding of the physical properties of PXX, a comparative study is performed for its analogue, that is, anthanthrene. By employing Marcus electron transfer theory coupled with an incoherent charge hopping and diffusion model, we estimate the charge mobilties of PXX and Ph-PXX. Our calculated results indicate that the introduction of a heteroatom (oxygen) at the reactive sites of anthanthrene can stabilize the extended π-system and improve the effiecient charge injection in electronic devices. The phenyl substitution of PXX makes a remarkable change of charge transport characteristics from a <i>p</i>-type semiconductor to an <i>n</i>-type semiconductor, which shed light on molecular design for an <i>n</i>-type semiconductor through simple chemical structural modification

    2‑(2-Hydroxyphenyl)benzimidazole-Based Four-Coordinate Boron-Containing Materials with Highly Efficient Deep-Blue Photoluminescence and Electroluminescence

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    Two novel four-coordinate boron-containing emitters <b>1</b> and <b>2</b> with deep-blue emissions were synthesized by refluxing a 2-(2-hydroxyphenyl)­benzimidazole ligand with triphenylborane or bromodibenzoborole. The boron chelation produced a new π-conjugated skeleton, which rendered the synthesized boron materials with intense fluorescence, good thermal stability, and high carrier mobility. Both compounds displayed deep-blue emissions in solutions with very high fluorescence quantum yields (over 0.70). More importantly, the samples showed identical fluorescence in the solution and solid states, and the efficiency was maintained at a high level (approximately 0.50) because of the bulky substituents between the boron atom and the benzimidazole unit, which can effectively separate the flat luminescent units. In addition, neat thin films composed of <b>1</b> or <b>2</b> exhibited high electron and hole mobility in the same order of magnitude 10<sup>–4</sup>, as determined by time-of-flight. The fabricated electroluminescent devices that employed <b>1</b> or <b>2</b> as emitting materials showed high-performance deep-blue emissions with Commission Internationale de L’Eclairage (CIE) coordinates of (<i>X</i> = 0.15, <i>Y</i> = 0.09) and (<i>X</i> = 0.16, <i>Y</i> = 0.08), respectively. Thus, the synthesized boron-containing materials are ideal candidates for fabricating high-performance deep-blue organic light-emitting diodes

    2‑(2-Hydroxyphenyl)benzimidazole-Based Four-Coordinate Boron-Containing Materials with Highly Efficient Deep-Blue Photoluminescence and Electroluminescence

    No full text
    Two novel four-coordinate boron-containing emitters <b>1</b> and <b>2</b> with deep-blue emissions were synthesized by refluxing a 2-(2-hydroxyphenyl)­benzimidazole ligand with triphenylborane or bromodibenzoborole. The boron chelation produced a new π-conjugated skeleton, which rendered the synthesized boron materials with intense fluorescence, good thermal stability, and high carrier mobility. Both compounds displayed deep-blue emissions in solutions with very high fluorescence quantum yields (over 0.70). More importantly, the samples showed identical fluorescence in the solution and solid states, and the efficiency was maintained at a high level (approximately 0.50) because of the bulky substituents between the boron atom and the benzimidazole unit, which can effectively separate the flat luminescent units. In addition, neat thin films composed of <b>1</b> or <b>2</b> exhibited high electron and hole mobility in the same order of magnitude 10<sup>–4</sup>, as determined by time-of-flight. The fabricated electroluminescent devices that employed <b>1</b> or <b>2</b> as emitting materials showed high-performance deep-blue emissions with Commission Internationale de L’Eclairage (CIE) coordinates of (<i>X</i> = 0.15, <i>Y</i> = 0.09) and (<i>X</i> = 0.16, <i>Y</i> = 0.08), respectively. Thus, the synthesized boron-containing materials are ideal candidates for fabricating high-performance deep-blue organic light-emitting diodes

    Coordination-Induced Conformational Control Enables Highly Luminescent Metallo-Cages

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    In recent years, luminescent materials have received a great deal of attention due to their wide range of applications. However, exploring a simple solution to overcome the fluorescence quenching resulting from the aggregation of conventional organic fluorophores remains a valuable area of investigation. In this study, we successfully constructed two metallo-cages, namely, SA and SB, through coordination-driven self-assemblies of the triphenylamine (TPA)-based donor L with different diplatinum(II) acceptors LA and LB, respectively. These metallo-cages take advantage of their steric nature and curved conformation to more effectively limit the free rotation of the benzene ring and hinder π–π stacking in the solid state, which successfully inhibited fluorescence quenching and realizing highly efficient luminescent properties. Therefore, this work offers a new design strategy for preparing materials with excellent luminescent properties

    A Highly Luminescent Metallo-Supramolecular Radical Cage

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    Luminescent metal-radicals have recently received increasing attention due to their unique properties and promising applications in materials science. However, the luminescence of metal-radicals tends to be quenched after formation of metallo-complexes. It is challenging to construct metal-radicals with highly luminescent properties. Herein, we report a highly luminescent metallo-supramolecular radical cage (LMRC) constructed by the assembly of a tritopic terpyridinyl ligand RL with tris(2,4,6-trichlorophenyl)methyl (TTM) radical and Zn2+. Electrospray ionization-mass spectrometry (ESI-MS), traveling-wave ion mobility-mass spectrometry (TWIM-MS), X-ray crystallography, electron paramagnetic resonance (EPR) spectroscopy, and superconducting quantum interference device (SQUID) confirm the formation of a prism-like supramolecular radical cage. LMRC exhibits a remarkable photoluminescence quantum yield (PLQY) of 65%, which is 5 times that of RL; meanwhile, LMRC also shows high photostability. Notably, significant magnetoluminescence can be observed for the high-concentration LMRC (15 wt % doped in PMMA film); however, the magnetoluminescence of 0.1 wt % doped LMRC film vanishes, revealing negligible spin-spin interactions between two radical centers in LMRC
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