Crystalline Perylene Research Articles

Carrier transport and mesomorphic properties of deformable fluorinated perylene bisimide bearing disiloxane chains

We synthesized liquid crystalline difluorinated perylene bisimide derivatives bearing oligosiloxane moieties. At room temperature, these compounds exhibited columnar phases which were stabilized thermodynamically, compared to that of a non-fluorinated analog. The absorption bands in the thin films of the fluorinated compounds exhibited a slight bathochromic shift compared to that in the solution state, indicating a weak electronic coupling between the fluorinated perylene bisimide cores in the columnar phases. The electron mobilities in the columnar phases of the difluorinated compounds were determined to be on the order of 10−2 cm2V−1s−1 at room temperature by the time-of-flight measurements. The LUMO levels of the difluorinated compounds were lowered by 0.1 eV from that of non-fluorinated analog. Anion radicals of the fluorinated compounds were stable as that of the non-fluorinated analog while dianions of the fluorinated compounds were unstable unlike that of the non-fluorinated analog. The difluorinated compounds was soft waxy solid. In particular, the 1,7-difluorinated derivative is deformable to form various shapes at room temperature. A study on the surface morphology of the thin film indicated formation of microscopic grooves, which should enhance the softness of the compound.

Superior electron mobility, red electroluminescence with high quantum efficiency from printable room temperature columnar liquid crystalline perylene bisimide

Synthesis of highly fluorescent compounds is currently a critical requirement to facilitate the economical and metal-independent manufacture of organic light-emitting diodes (OLEDs) on a large scale. This study presents a highly soluble, swallow tail based electron deficient perylene bisimide (PBIST) exhibiting room temperature columnar oblique (Colob) liquid crystalline behavior along with a high photoluminescence quantum yield, positioning itself as a promising candidate for efficient OLEDs. Incorporation of swallow tails helped in enhancing the solubility and reduction of the clearing points. This unique tailor-made molecular design with the liquid crystalline phase allowed a demonstration of n-type field effect mobility of 0.008 cm2 V−1s−1 when annealed in the liquid crystalline mesophase range (at 70 °C) which can be exploited in the fabrication of printable electronic devices. Capitalizing on the high charge transport and luminescence attributes of PBIST, a series of devices were fabricated by utilizing PBIST as a single emitter and dispersed at different concentrations of 0.3, 0.5 and 1 wt% in host material CBP. Impressively, doped devices featuring the CBP as a host at a 0.5 wt% PBIST concentration exhibited an external quantum efficiency (EQE) as high as 7 %, accompanied by a luminance of 1787 cd/m2. The high EQE is attributed mainly to the triplet–triplet annihilation (TTA) process. This notable EQE enhancement signifies a substantial stride towards expanding the utility of multifunctional columnar self-assembled materials for the advancement of OLEDs.

Bright green electroluminescence with an EQE of 4.6% from a host–guest OLED fabricated from an unsymmetric liquid crystalline N-annulated perylene ester imide as a dopant

Bay N-annulated perylene diester imide, with a swallow tail at one end and straight chains at the other end, exhibited a stabilized columnar hexagonal phase, and showed a bright green electroluminescence of 5269 cd m−2 and EQEmax of 4.6%.

Room Temperature Columnar Liquid Crystalline Perylene Bisimide as a Novel Corrosion Resistant Surface Film for Mild Steel Surface

The corrosion process can be seen as a widespread phenomenon, which is both pervasive and unstoppable. This is an undesirable phenomenon that reduces the life of materials and takes away their beauty. Potentiodynamic and electrochemical impedance tests are used to explore the corrosion inhibition abilities of a room temperature columnar liquid crystalline perylene bisimide (PBIO10) on mild steel (MS) samples in 1 M HCl. The inhibitor PBIO10 was demonstrated to be an outstanding corrosion inhibitor, with a maximum inhibition efficiency of 76%. In light of potentiometric polarization results, corrosion inhibition was achieved as the inhibitor getting adsorbed on the metal, and they fit into the category of anodic inhibitors. The protective layer was examined from SEM to confirm the protective coating generated on the MS surface. The increase in contact angle confirms the formation of a uniform layer on the MS surface. Analysis of the optical textures observed in POM, the nature of the mesophase under examination to columnar rectangular (Colr) phase. From the TGA, it was found that PBIO10 exhibits higher thermal stability u to 370 ℃. The density functional theory (DFT) and Monte Carlo simulation approach were used to investigate the relationship between molecular structure and inhibitory efficacy. The thermal behavior of PBIO10 was investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) studies. The phase transition from crystal to LC phase was at first examined with the help of POM observation.Graphical

High Photocatalytic Oxygen Evolution via Strong Built-In Electric Field Induced by High Crystallinity of Perylene Imide Supramolecule.

A highly crystalline perylene imide supramolecular photocatalyst (PDI-NH) is synthesized via imidazole solvent method. The catalyst shows a breakthrough oxygen evolution rate (40.6 mmol g-1 h-1 ) with apparent quantum yield of 10.4% at 400nm, which is 1353 times higher than the low crystalline PDI-NH. The highly crystalline structure comes from the ordered self-assembly process in molten imidazole solvent via π-π stacking and hydrogen bonding. Further, the excellent performance ascribes to the robust built-in electric field induced by its high crystallinity, which greatly accelerates the charge separation and transfer. What is more, the PDI-NH is quite stable and can be reused over 50 h without performance attenuation. Briefly, the crystalline PDI-NH with strong built-in electric field throws light on photocatalytic oxygen evolution, showing a new perspective for the design of organic photocatalysts.

Liquid-crystalline perylene bisimide derivatives bearing an azacrown ether ring complexing with alkaline metal ions

A polymerizable liquid crystalline perylene bisimide bearing a crown ether ring was synthesized. This compound form 1 : 1 complexes with lithium and sodium triflates, which exhibit columnar phases. Polymerized thin film indicated electrochromism in electrolyte solutions.

A Highly Crystalline Perylene Imide Polymer with the Robust Built-In Electric Field for Efficient Photocatalytic Water Oxidation.

A highly crystalline perylene imide polymer (Urea-PDI) photocatalyst is successfully constructed. The Urea-PDI presents a wide spectrum response owing to its large conjugated system. The Urea-PDI performs so far highest oxygen evolution rate (3223.9 µmol g-1 h-1 ) without cocatalysts under visible light. The performance is over 107.5 times higher than that of the conventional PDI supramolecular photocatalysts. The strong oxidizing ability comes from the deep valence band (+1.52 eV) which is contributed by the covalent-bonded conjugated molecules. Besides, the high crystallinity and the large molecular dipoles of the Urea-PDI contribute to a robust built-in electric field promoting the separation and transportation of photogenerated carriers. Moreover, the Urea-PDI is very stable and has no performance attenuation after 100 h continuous irradiation. The Urea-PDI polymer photocatalyst provides with a new platform for the use of photocatalytic water oxidation, which is expected to contribute to clean energy production.

Stabilization of ZnO quantum dots by preferred 1:2 interaction with a liquid crystal molecule

Zinc oxide (ZnO) quantum dots were synthesized in the presence of a columnar liquid crystalline perylene derivative. The liquid crystal molecules did not influence the nanoparticles' growth, and surprisingly they were efficient in stabilizing the colloidal dispersion over several months. For the first time, the quantity of ZnO units present in the ~4 nm sized ZnO nanoparticles was determined from the supramolecular interaction between the nanoparticles and the liquid crystal molecules as well as by analyzing the stoichiometry of the mixture. The quantity of ZnO units was also confirmed by theoretical studies performed by means of DFT calculations. The mixture was efficiently applied for methylene blue photodegradation.

Realizing lamellar nanophase separation in a double-cable conjugated polymer via a solvent annealing process

A double-cable conjugated polymer based on crystalline polythiophene backbone and perylene bisimide side units was developed to realize ordered lamellar structures via solvent annealing process.

Blends of Two Perylene Derivatives: Mesogenic Properties and Application As Emitter Materials in OLEDs

Blends consisting of two components, namely a liquid crystalline perylene ester and a bilaterally extended perylene ester, were studied. The liquid crystalline properties of these blends were investigated in detail by means of polarized optical microscopy and differential scanning calorimetry. The resulting phase diagram was used to explore the potential of these blends as emitter layers in OLEDs, which were prepared via thermal evaporation in a vacuum and spin coating of solutions.

Self-assembly of multi-stranded perylene dye J-aggregates in columnar liquid-crystalline phases

Many discoid dyes self-assemble into columnar liquid-crystalline (LC) phases with packing arrangements that are undesired for photonic applications due to H-type exciton coupling. Here, we report a series of crystalline and LC perylene bisimides (PBIs) self-assembling into single or multi-stranded (two, three, and four strands) aggregates with predominant J-type exciton coupling. These differences in the supramolecular packing and optical properties are achieved by molecular design variations of tetra-bay phenoxy-dendronized PBIs with two N–H groups at the imide positions. The self-assembly is driven by hydrogen bonding, slipped π–π stacking, nanosegregation, and steric requirements of the peripheral building blocks. We could determine the impact of the packing motifs on the spectroscopic properties and demonstrate different J- and H-type coupling contributions between the chromophores. Our findings on structure–property relationships and strong J-couplings in bulk LC materials open a new avenue in the molecular engineering of PBI J-aggregates with prospective applications in photonics.

On the possibility of singlet fission in crystalline quaterrylene.

Singlet fission (SF), the spontaneous down-conversion of a singlet exciton into two triplet excitons residing on neighboring molecules, is a promising route to improve organic photovoltaic (OPV) device efficiencies by harvesting two charge carriers from one photon. However, only a few materials have been discovered that exhibit intermolecular SF in the solid state, most of which are acene derivatives. Recently, there has been a growing interest in rylenes as potential SF materials. We use many-body perturbation theory in the GW approximation and the Bethe-Salpeter equation to investigate the possibility of intermolecular SF in crystalline perylene and quaterrylene. A new method is presented for determining the percent charge transfer (%CT) character of an exciton wave-function from double-Bader analysis. This enables relating exciton probability distributions to crystal packing. Based on comparison to known and predicted SF materials with respect to the energy conservation criterion (ES-2ET) and %CT, crystalline quaterrylene is a promising candidate for intermolecular SF. Furthermore, quaterrylene is attractive for OPV applications, thanks to its high stability and narrow optical gap. Perylene is not expected to exhibit SF; however, it is a promising candidate for harvesting sub-gap photons by triplet-triplet annihilation.

Low-lying excited states in crystalline perylene

Organic materials are promising candidates for advanced optoelectronics and are used in light-emitting diodes and photovoltaics. However, the underlying mechanisms allowing the formation of excited states responsible for device functionality, such as exciton generation and charge separation, are insufficiently understood. This is partly due to the wide range of existing crystalline polymorphs depending on sample preparation conditions. Here, we determine the linear optical response of thin-film single-crystal perylene samples of distinct polymorphs in transmission and reflection geometries. The sample quality allows for unprecedented high-resolution spectroscopy, which offers an ideal opportunity for judicious comparison between theory and experiment. Excellent agreement with first-principles calculations for the absorption based on the GW plus Bethe-Salpeter equation (GW-BSE) approach of many-body perturbation theory (MBPT) is obtained, from which a clear picture of the low-lying excitations in perylene emerges, including evidence of an exciton-polariton stopband, as well as an assessment of the commonly used Tamm-Dancoff approximation to the GW-BSE approach. Our findings on this well-controlled system can guide understanding and development of advanced molecular solids and functionalization for applications.

High pressure tuning the geometrical and electronic structures of perylene

This study concentrates on the geometrical and electronic structural properties of perylene (C20H12) at high pressure as a representative of polycyclic aromatic hydrocarbons family. The pressure effects on the lattice parameters, the electronic band structures and energy gap of crystalline perylene are calculated up to 20 GPa by performing density functional calculations. The lattice parameters a, b and c are decreases by 1.94 (−17.1%), 1.64 (−15.1%), and 1.26 (−12.2%), respectively, while the monoclinic angle β are decreased by 8.70 in this pressure region. At 20 GPa the unit cell volume is decreased by 50%. The bulk modulus B0 and its pressure derivative are fitted from the volume-pressure relation. Moreover, the evolution of the electron band structure, the total density of states (DOS) and partial density of states (PDOS) at high pressure are also presented.

Structure and electronic properties of perylene and coronene under pressure: First-principles calculations

The structural and electronic properties of crystalline perylene and coronene have been investigated within the framework of density functional theory including van der Waals interactions. The investigation of β, γ and dimeric form of polycyclic aromatic hydrocarbons allowed for study of relationship between molecular arrangement and band structure. The computed lattice parameters have good agreement with experimental data. I study on the structural and electronic properties of the crystals under the hydrostatic pressure of 0–20GPa. The predicted results are compared with each other. It has been established that pressure has different effect on γ- and β-form of the coronene. The values of the bulk moduli of crystals are in the range 9–11GPa. The all crystals have indirect band gap.

3b14 オリゴシロキサン鎖を有するペリレンテトラカルボン酸ビスイミドの配向処理(分子配向エレクトロニクス,口頭発表,2013年日本液晶学会討論会)

3b14 オリゴシロキサン鎖を有するペリレンテトラカルボン酸ビスイミドの配向処理(分子配向エレクトロニクス,口頭発表,2013年日本液晶学会討論会)

The influence of the nematic phase on the phase separation of blended organic semiconductors for photovoltaics

Differential scanning calorimetry in combination with atomic force microscopy is used to examine the phase separation of a blended nematic liquid crystalline electron-donor and crystalline perylene electron-acceptor mixture. Separate domains of donor and acceptor material are mostly retained in the blend, although a small proportion of the acceptor, increasing with increasing donor concentration, is mixed in with the donor domains. Annealing in the nematic phase allows the donor and acceptor molecules to move and generate phase-separated domains of the required size, thus enhancing the performance of bulk heterojunction photovoltaic devices based on these blends. We show that the optimum annealing temperature can be controlled by manipulation of the temperature range of the nematic phase of the donor.

Structural and electronic properties of perylene from first principles calculations

The electronic structure of crystalline perylene has been investigated within the framework of density functional theory including van der Waals interactions. The computations of the lattice parameters and cohesive energy have good agreement with experimental values. We have also calculated the binding distance and energy of perylene dimers, using different schemes, which include van der Waals interactions.

2b03 オリゴシロキサン鎖を有するペリレンテトラカルボン酸ビスイミドの液晶性と電子輸送性(分子配向エレクトロニクス,口頭発表,2012年日本液晶学会討論会)

2b03 オリゴシロキサン鎖を有するペリレンテトラカルボン酸ビスイミドの液晶性と電子輸送性(分子配向エレクトロニクス,口頭発表,2012年日本液晶学会討論会)

Liquid–crystalline perylene tetracarboxylic acid bisimide bearing oligosiloxane chains with high electron mobility and solubility

Liquid–crystalline perylene tetracarboxylic acid bisimide derivatives 1 and 2 bearing 1,1,1,2,2,3,3-heptamethyltrisiloxane chains at the end of alkyl side-chains have been synthesized. Compound 1 having four trisiloxane chains exhibits a hexagonal columnar phase at room temperature. Time-of-flight measurement reveals that the electron mobility in the columnar phase of compound 1 exceeds 10−3cm2V−1s−1 at room temperature. In contrast, compound 2 bearing two trisiloxane chains is not mesomorphic. These two compounds are soluble in various organic solvents except for alcohols and thin films can be produced by a spin-coating method.