Organic Single Crystals Research Articles

Luminescent Möbius Strip of a Flexible Halogen-Bonded Cocrystal Evolved from Ring and Helix.

Luminescent Möbius strip microstructures have been created for the first time based on flexible organic single crystals via a template-free solution self-assembly. We herein demonstrated a rationally designed morphological evolution toward Möbius strips from rings and helixes. Our findings lay the foundation for the future construction of complex matters with predetermined morphologies and functions from crystal systems.

Directed self-assembly of organic crystals into chip-like heterostructures for signal processing

Organic single crystals show broad application prospects in the field of optical confinement and waveguides due to their low optical transmission loss and tunable optical properties. Individual one- or two-dimensional (1D or 2D) optical waveguide crystals have the limitations of a single function in organic photonics. In this work, a chip-like organic heterostructure was fabricated using an elaborately designed, sequential growth method. By regulating the concentration of each organic component, the processes of solution self-assembly, etching, and epitaxial self-assembly are successively performed to complete the directional growth of organic micro/nanostructures. Notably, the as-prepared chip-like organic heterostructure is composed of 1D/2D optical waveguide crystals, which can realize multidimensional photon transportation and multi-terminal directional optical signal output. Furthermore, the unique 2D optical waveguide properties of the chip-like heterostructures offer opportunities for constructing the encoding form of the output optical signal at the micro/nanoscale.

Vapor‐Phase Growth Strategies of Fabricating Organic Crystals for Optoelectronic Applications

AbstractVapor‐phase growth methods, taking the advantages of producing high‐quality crystals with low defects, thin thickness, and homogeneous composition, are of great significance in the field of organic crystal growth and their high‐performance applications. At present, the requirements for organic crystals as building blocks for the construction of optoelectronic devices are increasing with the constant advances in organic optoelectronics. Therefore, the vapor‐phase growth method would become one of the practical techniques that cannot be ignored to fabricate organic crystals. In this paper, an overview of different vapor‐phase growth methods for the preparation of organic single crystals is provided. An introduction to the current status of the vapor phase method is presented and the view on the challenges it faces with some promising solution ideas. It is believed that this review will serve as a reference for further development and an inspiration for the new way forward.

Nucleation in situ of perylene crystal by femtosecond laser induced cavitation

Organic semiconductor single crystal materials have broad application prospects in the field of high-performance optoelectronic devices because of their highly ordered structure, few defects, and high carrier mobility. However, it is difficult to control the nucleation location of crystal formation in the current commonly used crystal growth methods including physical vapor transport and solution processing, which makes it difficult to manufacture organic crystal devices. Laser-induced crystallization technology is expected to solve this problem. In this study, we demonstrated nucleation in situ of a perylene crystal by femtosecond laser induced cavitation. The results show that the crystallization of perylene crystals induced by the femtosecond laser is mainly due to the aggregation effect by laser cavitation bubbles caused by multiphoton absorption. This strategy facilitates the application of organic single crystals to optoelectronic devices.

Growth, physico-chemical properties, opto-electrical characteristics, thermo-mechanical and DFT studies of 4-aminoantipyrine single crystals

The aim of this work was to grow organic single crystals of 4-Aminoantipyrine (4-AAP) under ambient conditions, using a solvent slow evaporation method, and then to investigate the crystal structure, optical band gap, optical transmittance behavior, second harmonic generation efficiency, thermal stability, material rigidity, and dielectric responses for opto-electrical based device applications. The powder X-ray diffraction (XRD) and single crystal XRD analyzes revealed the hexagonal crystal structure and lattice parameter values of the as-grown 4-AAP. The respective molecular vibration bands and functional groups of the as-grown 4-AAP were identified using the experimental and theoretical FT-IR analysis. The optical absorption and transmittance spectrum of the 4-AAP single crystals revealed good transparency throughout the visible region. The non-linear optical (NLO) characteristics of the 4-AAP crystals were tested using the Kurtz and Perry powder technique. Thermal gravimetric (TGA) and differential thermal analysis (DTA) were used on the as-grown crystals, to determine their weight loss and heat absorption/release process. The hardness vs load plot can be used to determine the hardness values and response of the hard as-grown 4AAP crystals under the influence of load. The electrical conductivity and dielectric behavior of the 4-AAP crystals changed as the applied frequency increased. Computational techniques were used to investigate the 4-AAP's optimized geometrical structure, theoretical optical band, molecular electrostatic potential, and Mulliken atomic charge population.

Ambipolar Organic Field‐Effect Transistors and Complementary Circuits Based on Single Crystals with Alcohol Treatment

AbstractAmbipolar organic field‐effect transistors (OFETs) are promising candidates for compact organic complementary circuits. High and balanced ambipolar mobilities that facilitate high operation speed and simplifying layout designs, as well as symmetric electrodes that minimize fabrication complexity are critical integrities for state‐of‐art ambipolar OFETs. Organic single crystals with intrinsic ambipolar characteristics are ideal active layer materials because of the high molecular ordering and low density of defects, whereas the generally low electron mobility hindered their further implantation. In this work, the highly crystallized 6,13‐bis(triisopropylsilylethynyl) pentacene single crystals are employed and successfully unveiled the intrinsic high electron mobility by a facile alcohol treatment approach. The resulting ambipolar OFETs showed averaged hole and electron mobilities both higher than 1 cm2 V−1 s−1 by a single type of metal electrode. The presented ambipolar OFETs not only improved the static and dynamic performance of ambipolar OFET‐based complementary inverters and ring oscillators by showing a high voltage gain of 186 and a short stage delay time of 0.7 ms, but they also allowed one logic gate to show two logic functions and potentially benefit the design and functionalities of future OFET‐based complementary circuits as well.

Challenging Bendable Organic Single Crystal and Transistor Arrays with High Mobility and Durability toward Flexible Electronics.

Bendable organic single crystals are promising candidates for flexible electronics owing to their superior charge-transport properties. However, large-area high-quality organic single crystals are rarely available on the polymer substrates generally used in flexible electronics. Here, a surface-assisted assembly strategy based on a polymer modification, poly(amic acid) (PAA), is developed to grow large-area organic singe crystals on polymer substrates using a simple drop-casting method. The unique surface properties of PAA that enable molecular solution superwetting and promote molecular ordered assembly produce an extraordinary self-driven "meniscus-guided coating" behavior, enabling the fabrication of millimeter-sized, highly aligned organic single crystals for a variety of organic semiconductors. Organic field-effect transistors based on a mode molecule of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene demonstrate the highest (average) mobility of 18.6 cm2 V-1 s-1 (15.9 cm2 V-1 s-1 ), attractively low operating voltage of -3V, and high flexible durability. The results shed light on the large-area fabrication of organic single crystals on polymer dielectrics toward high-performance and integrated plastic electronics.

An elastic organic single crystal with bending and high pressure-induced fluorochromism properties

The mechanically tunable flexible fluorochromic elastic organic single crystals are extremely rare. Fortunately, we prepared a needle-like elastic crystal (TPABA) with bending and high pressure-induced fluorochromism properties. With the reversible change of hydrostatic pressure, the crystal fluorescence underwent reversible red-shift and blue-shift (wavelength change greater than 100 nm). Interestingly, upon bending, the inner and outer arcs on the (002) and (200) surfaces of the crystal exhibited distinct fluorochromic effects by spatially resolved μ-PL measurements. Upon bending, the fluorescence emission of the inner and outer arcs on the (002) face of the crystal was red-shifted and blue-shifted by 26 nm and 4 nm, respectively. Different from (002) face, the inner arc and outer arc of the crystal (200) plane were only blue-shifted and red-shifted by 2 nm and 3 nm, respectively. Theoretical calculations indicated that, on the one hand, with the reversible bending of the crystal, the intermolecular interaction force distance in the crystal would change reversibly, and the corresponding inner and outer arc fluorescence emission wavelengths of the crystal plane would reversibly change. On the other hand, the number of π-π interactions on each face of the crystal had an important effect on the bending-induced fluorochromism of the crystal. This paper provided new idea for the preparation of the multi-faceted bending fluorochromism flexible crystals.

Prediction of the Mechanical Deformation Properties of Organic Crystals Based upon their Crystallographic Structures: Case Studies of Pentaerythritol and Pentaerythritol Tetranitrate.

Development of a quantitative model and associated workflow for predicting the mechanical deformation properties (plastic deformation or cleavage fracture) of organic single crystals from their crystallographic structures using molecular and crystallographic modelling. Intermolecular synthons, hydrogen bonding, crystal morphology and surface chemistry are modelled using empirical force fields with the data integrated into the analysis of lattice deformation as computed using a statistical approach. The approach developed comprises three main components. Firstly, the identification of the likely direction of deformation based on lattice unit cell geometry; secondly, the identification of likely lattice planes for deformation through the calculation of the strength and stereochemistry of interplanar intermolecular interactions, surface plane rugosity and surface energy; thirdly, identification of potential crystal planes for cleavage fracture by assessing intermolecular bonding anisotropy. Pentaerythritol is predicted to fracture by brittle cleavage on the {001} lattice planes by strong in-plane hydrogen-bond interactions in the <110>, whereas pentaerythritol tetranitrate is predicted to deform by plastic deformation through the slip system {110} < 001>, with both predictions being in excellent agreement with known experimental data. A crystallographic framework and associated workflow for predicting the mechanical deformation of molecular crystals is developed through quantitative assessment of lattice energetics, crystal surface chemistry and crystal defects. The potential for the de novo prediction of the mechanical deformation of pharmaceutical materials using this approach is highlighted for its potential importance in the design of formulated drug products process as needed for manufacture by direct compression.

Electrical, optical, and mechanical properties of modified Czochralski grown organic 4-nitrobenzaldehyde single crystal

Growing large crystals of organic compounds with low melting points is a challenge but it was resolved by suitable modifications of the Czochralski (CZ) technique in the present study. A nonlinear optical single crystal of 4-nitrobenzaldehyde (4-NB) with a cylindrical shape, length of 2.5 cm, and diameter of 3 mm was successfully grown using an inexpensive modified CZ crystal growth technique at a temperature of 106 °C. The crystal structure and lattice parameters of the as-grown crystal were determined by single crystal and powder X-ray diffraction analyses. Intermolecular interactions were studied in the 4-NB crystal based on the Hirshfeld surface and two-dimensional fingerprint plot. The presence of various functional groups in the as-grown crystal was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance (1H and 13C) spectroscopy. The thermal behavior of the 4-NB crystal was analyzed by thermogravimetric analysis and differential thermal analysis. High transparency (75%) with an optical band gap of 3.34 eV and lower cut-off of 370 nm were confirmed by ultraviolet–visible–near infrared spectroscopy. The temperature-dependent dielectric behavior was determined for the 4-NB crystal at a constant frequency of 5 kHz. The mechanical properties of the 4-NB single crystal were analyzed based on the Vickers microhardness and void analysis, which confirmed the soft nature of the crystal. The modified CZ technique allowed us to obtain disk-shaped organic 4-NB crystals for use in optical applications.

Intrinsic Linear Dichroism of Organic Single Crystals toward High‐Performance Polarization‐Sensitive Photodetectors (Adv. Mater. 22/2022)

Polarization-Sensitive Photodetectors High-performance polarization-sensitive organic photodetectors with a linear dichroic ratio as high as 1.9 are successfully developed by Huanli Dong, Zhongming Wei, Liqiang Li, Wenping Hu, and co-workers, as described in article number 2105665, utilizing the intrinsic anisotropic nature of organic semiconductor single crystals. These devices show new opportunities for using organic semiconductors to develop highly compact polarization-sensitive photodetectors in diverse applications, and open up a new area for the study of organic semiconductors.

Low-power high-mobility organic single-crystal field-effect transistor

Evolving flexible electronics requires the development of high-mobility and low-power organic field-effect transistors (OFETs) that are crucial for emerging displays, sensors, and label technologies. Among diverse materials, polymer gate dielectrics and two-dimensional (2D) organic crystals have intrinsic flexibility and natural compatibility with each other for OFETs with high performance; however, their combination lacks non-impurity and non-damage construction strategies. In this study, we developed a desirable OFET system using damage-free transfer of 2D organic single crystal, dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene on a unique polymer dielectric layer, poly(amic acid) (PAA). Benefiting from the unique PAA surface nanostructure and the long-range ordered characteristics of the 2D organic single crystal, the resulting OFETs show remarkable performance with high mobility and low operating voltage of 18.7 cm2 V−1 s−1 and −3 V, respectively. The result indicates that combining polymer gate dielectric with 2D organic single crystal using a high-quality method can produce flexible electronic devices with high performance.

Multi-faceted bending and multi-directional flexible optical waveguide of the elastic organic single crystal

Multi-faceted bending elastic organic single crystals are extremely rare and have potential applications in optical communication, mechanically tunable flexible fluorochromic materials, etc., which have attracted great attention of researchers. Herein, we reported two compounds with simple structures, namely 1,3-dimethylbarbituric acid (DMBA) and its derivative (TPABA). Under stress, both (200) and (002) faces of TPABA crystal could undergo reversible elastic deformation, possessing rare multi-faceted bending properties. The abundant weak isotropic intermolecular interactions (such as H-bonding, etc.) in crystal could buffer mechanical stress and prevent crystal fracture. Fortunately, TPABA crystals showed multi-directional flexible optical waveguide characteristics. The corresponding optical loss coefficients were 0.57 dBmm−1 (582 nm, straight line), 0.75 dBmm−1 (583 nm, (002) face bending), and 0.58 dBmm−1 (587 nm, (200) face bending). Unlike TPABA crystals, under stress, the (040) and (200) faces of the DMBA crystal underwent plastic deformation and fracture, respectively, showing the characteristics of single-faceted plastic deformation.

Real Temperature Model of Dynamic Disorder in Molecular Crystals.

Charge carrier mobilities in ordered organic semiconductors are limited by inherent vibrational phonons that scatter carriers. To improve a material's intrinsic mobility, restricting particularly detrimental modes with molecular substitutions may be a viable strategy. Here, we develop a probabilistic temperature-dependent displacement model that we couple with the density functional dimer projection protocol to predict effective electronic coupling fluctuations. The phonon-induced deviations from the equilibrium electronic couplings are used to infer the detriment of low-frequency phonons on charge carrier mobilities in a set of organic single crystals. We show that asymmetric sliding motions in pentacene and 2,6-diphenylanthracene induce large electronic coupling fluctuations, whereas seesawlike motions cause large fluctuations in rubrene, 9,10-diphenylanthracene, and, 2,6-diphenylanthracene. Vibrational analyses revealed that the asymmetric sliding phonon in rubrene persists only in the low-mobility direction of the crystal. Therefore, rubrene's intrinsic high mobility is likely due to the absence of this source of disorder in its high-mobility conduction channels. This model can be used to identify particularly harmful or helpful phonons in crystalline materials and may provide design rules for developing materials with intrinsically low disorder.

Growth Pattern Control and Nanoarchitecture Engineering of Metal-Organic Framework Single Crystals by Confined Space Synthesis.

The nanoarchitecture engineering of metal–organic frameworks (MOFs) is a fascinating but intellectually challenging concept that opens up avenues for both tailoring the properties of MOFs and expanding their applications. Herein, we report the confined growth of ZIF-8 single crystals in a three-dimensionally ordered (3DO) macroporous polystyrene replica and reveal that their growth patterns, morphologies, and nanoarchitectures can be highly engineered using the concentration of the precursor. Impressively, the favorable in situ confined growth enables the successful fabrication of 3DO sphere-assembled ZIF-8 single crystals or 3DO single-crystalline ZIF-8 sphere arrays when a low- or high-concentration precursor solution, respectively, is used as the feedstock. Furthermore, our strategy can be extended to the preparation of other 3DO MOF single crystals, including ZIF-67 and HKUST-1, with similar controllable hierarchical nanoarchitectures. With the successful preparation of a series of diameter-tunable ZIF-8 single-crystalline spheres, we further unravel their interesting size–performance relationship in the Knoevenagle reaction between benzaldehyde and malononitrile, wherein the smallest spheres show the fastest first-order reaction kinetics. This study not only develops a general strategy for engineering the nanoarchitectures of MOF single crystals but also provides fundamental knowledge of the mechanism for the growth of hierarchical single crystals under confined spaces.

Structural, thermal, linear and nonlinear optical and cytotoxicity studies of a novel organic stilbazolium salt: 4-[2-(4-hydroxyphenyl)ethenyl]-1-methylpyridinium 4-styrenesulfonate

Organic non-linear single crystals of 4-[2-(4-hydroxyphenyl)ethenyl]-1-methylpyridinium 4-styrenesulfonate (HMSS) are grown by means of slow solvent evaporation growth process. Stoichiometric ratio of the elements existing in the compound is identified by elemental analysis. Single crystal X-ray diffraction discloses that the developed crystal being included in to P21/n space group with monoclinic crystal system. In addition, an analysis of crystal structure and Hirshfeld surface are used to expose the intermolecular interaction and hydrogen bonds. Quantum chemical calculations performed using the density functional theory (DFT) at DFT/B3LYP/6–311+G(d,p) level of the compound provides further insight on the properties in particular molecular electrostatic potential, natural bonding orbital analysis (NBO), Mulliken and NPA charges, static dipole moment, polarizability, first order hyperpolarizability and thermodynamic functions. The frequencies (vibrational) of the compound HMSS are recognized using FT-IR and FT-Raman analysis and compared with the calculated data. Thermal properties of HMSS are accomplished via the way of TG and DSC analyses. Further, antiproliferative behavior of the obtained compound is assayed against human breast adenocarcinoma cells MCF 7 and normal Vero cells (monkey's kidney cells).

Investigations on synthesis, growth and physicochemical properties of organic nonlinear optical crystal: 2-aminopyridinium maleate

Organic nonlinear optical single crystal of 2-aminopyridinium maleate (2APM) was grown using a slow evaporation method. The single crystal X-ray diffraction study reveals that the crystals possess to monoclinic system with acentric space group Pc. The Fourier Transform Infrared spectrum is used to identify the sample functional group. Lower cutoff wavelengths have been seen down to 342 nm and the direct optical band gap has been calculated to be 5.9 eV in this region of the spectrum. The microhardness of the 2APM sample was refined using a Vicker's microhardness tester under matching stress. DSC analysis was used to assess the crystal thermal stability. The 2APM crystal dielectric behavior was investigated over a range of frequencies. The Nd: YAG laser was utilized to create the second harmonic waveform. The 2APSS crystal emission spectrum was uncovered during a photoluminescence experiment. Third-order nonlinear susceptibility χ(3) = 5.741 x 10−8 of 2APM formed crystal was utilized to estimate the values for third-order NLO exploits.

Effect of Aromatic Solvents Residuals on Electron Mobility of Organic Single Crystals

AbstractBalanced electron and hole transport properties are essential for various organic electrical/optoelectrical applications such as organic solar cells, complementary circuits, and light‐emitting transistors. However, the electron transport in organic semiconductor lags far behind the hole side, making it with vital significance to seek the factors that limit the electron mobility. Here, the authors demonstrate that the π‐conjugated solvents, as essential components in the widely‐used solution processing techniques, can significantly suppress the electron transport if they are not properly removed and trapped as residuals. Single crystals of typical p‐type materials exhibit a transition from p‐type behavior to ambipolar conductance via reducing the amount of solvent residuals, and the same effect is confirmed by varied p‐type materials and solvents. The highest electron mobility reaches 0.027 cm2 V−1 s−1 and 0.029 cm2 V−1 s−1 for 6,13‐bis(triisopropylsilylethynyl)pentacene and 5,15‐bis(triisopropylsilylethynyl)tetrabenzoporphyrin, respectively. This work discloses the non‐negligible existence of solvent residuals even in high quality, long‐range ordered organic single crystals, and further provides efficient strategies to harvest the n‐type behaviors of organic semiconductor materials.

Growth, linear and nonlinear optical property and dielectric studies of an efficient organic ionic single crystal: 2-amino-5-methyl-pyridinium trifluoroacetate for optoelectronic devices

Growth, linear and nonlinear optical property and dielectric studies of an efficient organic ionic single crystal: 2-amino-5-methyl-pyridinium trifluoroacetate for optoelectronic devices

Structural Elucidation, Growth and Characterization of (E)-2-(4-dimethylamino) benzylidine-3, 4-dihyronapthalen-1(2H) -one Single Crystal for Nonlinear Optical Applications

A novel third order nonlinear organic single crystal (E)-2-(4-dimethylamino) benzylidine-3, 4-dihyronapthalen-1(2H)-one (DMBH) which adapts to triclinic space group P21/n is crystallized by slow evaporation technique. Comprehensive investigations on linear optical properties have been performed. The thermal stability without any loss of weight has been performed. The molecular structure of DMBH was confirmed by 1H NMR and 13C NMR analysis. DMBH exhibits minimal activation energy value which makes it suitable for device fabrication. Further B3LYP/6-31G++ level has been used theoretically to obtain optimized geometry, vibrational frequency, static first-order hyperpolarizability parameter. The functional groups of FT-IR and FT-Raman were compared with experimental and theoretical results and it was found to be in good concordance. Electron Localization Function (ELF) and Localized Orbital Locator (LOL) were attained from Multiwfn software to study the reactive sites of DMBH. Natural Bond Orbital (NBO) levels help to understand the delocalization of the charges in DMBH. LDT (Laser Damage Threshold) studies proclaim the suitability of the title compound for nonlinear optical applications. The experimental and theoretical reports suggest that DMBH is 406 times better than urea and other chalcone derivatives.