Organic Single Crystals Research Articles

Studies on the growth and characterization of a new organic nonlinear optical single crystal: 2-amino 5-methyl-pyridinium 4-methoxybenzoate for optoelectronic and photonic devices

Single crystals of an efficient nonlinear optical material 2-amino 5-methylp yridinium 4-methoxybenzoate (2A5MP4MB) have been grown successfully from the aqueous solution by slow evaporation technique. Single crystal XRD reveals that the crystal belongs to monoclinic system with the space group P21/c. The various functional groups present in the material were ascertained by FT-IR spectral studies. The UV–Visible NIR spectrum of 2A5MP4MB shows excellent transmittance in the entire UV visible and near IR region with a lower cut off wavelength of 269 nm. The photoluminescence spectrum confirms the photon excitation process and wide band gap of the 2A5MP4MB crystal. The dielectric study on 2A5MP4MB crystal reveals normal dielectric behavior and the optical quality of the grown crystal for device applications. The laser damage threshold value of 2A5MP4MB crystal was estimated to be 4.11 GW/cm2. The third-order nonlinear optical parameters were calculated by Z-scan technique using 532 nm diode pumped CW Nd: YAG Laser and the results of the studies are discussed detail in this paper.

Organic single‐crystal light‐emitting transistors with external quantum efficiency over 20%

AbstractOrganic light‐emitting transistors (OLETs) have attracted increasing attention because of their potential applications in next‐generation displays and high‐energy operating devices. However, the simultaneous achievement of high luminescent efficiency and carrier mobility in organic semiconductors remains challenging because the localized excitons are advantageous for light emission, whereas the delocalized carriers are beneficial for efficient charge migration. Herein, we report an organic single crystal of a cyano‐substituted styrene derivative with balanced mobility yielding a record‐high external quantum efficiency of 20.5% in OLETs. Temperature‐dependent I–V curves and electronic structure analyses based on first‐principles calculations were performed to disclose the underlying mechanism as a band transport, which provides an efficient way to achieve high quantum efficiency in OLETs.

Circularly polarized electroluminescence from a single-crystal organic microcavity light-emitting diode based on photonic spin-orbit interactions

Circularly polarized (CP) electroluminescence from organic light-emitting diodes (OLEDs) has aroused considerable attention for their potential in future display and photonic technologies. The development of CP-OLEDs relies largely on chiral-emitters, which not only remain rare owing to difficulties in design and synthesis but also limit the performance of electroluminescence. When the polarization (pseudospin) degrees of freedom of a photon interact with its orbital angular momentum, photonic spin-orbit interaction (SOI) emerges such as Rashba-Dresselhaus (RD) effect. Here, we demonstrate a chiral-emitter-free microcavity CP-OLED with a high dissymmetry factor (gEL) and high luminance by embedding a thin two-dimensional organic single crystal (2D-OSC) between two silver layers which serve as two metallic mirrors forming a microcavity and meanwhile also as two electrodes in an OLED architecture. In the presence of the RD effect, the SOIs in the birefringent 2D-OSC microcavity result in a controllable spin-splitting with CP dispersions. Thanks to the high emission efficiency and high carrier mobility of the OSC, chiral-emitter-free CP-OLEDs have been demonstrated exhibiting a high gEL of 1.1 and a maximum luminance of about 60000 cd/m2, which places our device among the best performing CP-OLEDs. This strategy opens an avenue for practical applications towards on-chip microcavity CP-OLEDs.

Organic photodetectors based on pentacene single crystals with fast response and flexibility

Organic single crystals (OSCs) have attracted increasing interest in advanced optoelectronic devices, in particular for flexible and wearable devices, due to their high carrier mobility and intrinsic mechanical flexibility.

Strong light-matter coupling in pentacene thin films on plasmonic arrays.

Utilizing strong light-matter coupling is an elegant and powerful way to modify the energy landscapes of excited states of organic semiconductors. Consequently, the chemical and photophysical properties of these organic semiconductors can be influenced without the need of chemical modification but simply by implementing them in optical microcavities. This has so far mostly been shown in Fabry-Pérot cavities and with organic single crystals or diluted molecules in a host matrix. Here, we demonstrate strong, simultaneous coupling of the two Davydov transitions in polycrystalline pentacene thin films to surface lattice resonances supported by open cavities made of silver nanoparticle arrays. Such thin films are more easily fabricated and, together with the open architecture, more suitable for device applications.

High-performance ultra-low-voltage organic field-effect transistors based on anodized TiOx dielectric and solution-sheared organic single crystals

An optimal solution for achieving ultra-low-voltage (at 1 V) organic field-effect transistors using an anodized TiOx/PS hybrid dielectric combined with a solution-sheared organic single-crystal thin film is demonstrated.

Crystal photonics foundry: geometrical shaping of molecular single crystals into next generation optical cavities.

The advancements in organic photonics have reached new heights in the recent past with the demonstration of diverse organic crystal optical components and circuits. However, the development of industrially viable manufacturing of organic optical components is the need of the hour for finding an alternative to silicon-based photonics. Here, we demonstrate focused ion beam (FIB) milling as a tool to shape organic single crystals into optical cavities of diverse geometries and dimensions. The generality of FIB milling was tested on perylene and coumarin-153 microcrystals. The microcrystals obtained by self-assembly of perylene and sublimation of coumarin-153 were carved into desired disc-, ring- and rectangular shapes. These shaped crystals act as cavities exhibiting sharp resonance modes in the fluorescence spectrum, confirming optical interference. The FDTD numerical calculations support the light electric field distribution in these optical cavities. This unprecedented single crystal processing technique enables industrial-scale production of optical components and circuits and acts as a foundry for crystal photonics.

Synthetic pathway of 2-fluoro-N,N-diphenylbenzamide with opto-electrical properties: NMR, FT-IR, UV-Vis spectroscopic, and DFT computational studies of the first-order nonlinear optical organic single crystal

Abstract 2-Fluoro-N,N-diphenylbenzamide (2FNNDPBA), a natural nonlinear optical (NLO) single crystal, was incorporated from diphenylamine utilizing 2-fluoro benzoyl chloride as a side chain. The single crystals were successfully developed by a slothful evaporation arrangement approach utilizing ethyl acetate as a dissolvable solvent at room temperature. The synthesized compound fragmented ion peak (m/z = 291) was affirmed by gas-chromatographic mass spectrometry investigation. The unit cell dimensions were assessed using single-crystal X-ray diffraction analysis, which reveals that the crystals possess the orthorhombic system with space group Pbca. The existence of proton and carbon in a compound was affirmed by 1H and 13C nuclear magnetic resonance. The functional groups therein of 2FNNDPBA have been identified from FT-IR and FT-Raman studies and amide carbonyl stretching frequency peak appeared at 1,662 cm−1. The lower cut-off wavelength of 2FNNDPBA is found to be 240 nm and the experimental and theoretical optical band gap was calculated as 3.21 and 3.1083 eV. The UV-Visible spectrum of 2FNNDPBA shows two high-flying peaks at 240 and 273 nm. Major weight losses were observed between 160°C and 275°C for the designated compound. The thermal property for 2FNNDPBA was estimated by thermogravimetric analysis/differential thermal analysis investigation, which shows immense thermal strength up to 171°C. Density functional theory method with Gaussian 09 software for theoretical investigations of 2FNNDPBA for Mulliken charge analysis, highest occupied molecular orbital–lowest-lying unoccupied molecular orbital, and molecular electrostatic potential properties has been analyzed. The SHG productivity was proved by Kurtz-Perry powder strategy and has an efficiency 2.22 times that of standard potassium dihydrogen phosphate. The laser damage threshold of 2FNNDPBA crystals was discovered to be 1.18 GW·cm−2. The hyperpolarizability simulations further show that the current material has an excellent NLO activity tendency. The melting point of the developed crystal is 158°C.

Repair and Splicing of Centimeter‐Size Organic Crystalline Optical Waveguides

AbstractOrganic single crystals that are capable of transmitting light and charge are quickly shaping into a new forefront of research in photoelectronic materials that is thought to hold a tremendous potential for the broader field of organic electronics. However, one of the main disadvantages that currently stands against the direct application of organic single crystals in that capacity is their pronounced proneness to mechanical damage due to brittleness, abrasion, and wear. To account for this drawback, here a simple and universal strategy is proposed for the recovery of macroscopic integrity of cracked or completely fractured crystals based on the layer‐by‐layer charged polymer assembly approach that can be used to effectively recover the damaged crystals. It is shown that in addition to being an effective means for reasonable restoration of their optical waveguiding ability, this approach can also be used to combine different crystals into hybrid organic photonic integrated circuits (OPICs) and even to construct dynamic hybrid OPICs as active and/or passive optical waveguides. The resulting integrated crystalline OPIC bundles act as optical waveguides for transmission of light with different colors and can also be used for light mixing to generate white light.

Synthesis, Structural Characterization and Theoretical NLO Activity of N-(4-Acetyl-5-(4-(Nitro) Phenyl)-4,5-Dihydro-1,3,4-Thiadiazol-2-yl)-N-Phenyl Acetamide

The special properties of organic compounds are due to the polyvalence of the carbon atom. In this research, the organic single crystal of N-(4-acetyl −5-(4-(nitro) phenyl) −4,5-dihydro-1,3,4-thiadiazol-2-yl) -N-phenylacetamide (NTDZ) was successfully synthesized and crystallized in isopropanol by using slow evaporation solution growth method. FT-IR, 1H and 13C NMR spectroscopic techniques were used to characterize the presence of various functional groups in the NTDZ molecular structure. Single crystal X-ray data have been collected and used for the structural determination of NTDZ. The title crystal crystallized in the monoclinic space group P21/c, according to X-ray analysis. Besides, quantum chemical studies were carried out using the density functional theory calculation method. The theoretical and experimental geometrical parameters were compared indicating a good accordance between them. Moreover, surface shapes were displayed using 3D-Hirshfeld surface analysis, and 2D-fingerprint graphs were used to quantify the contributions of C–H…O and C–H…N intermolecular interactions. Furthermore, the vibration spectrum of the NTDZ is calculated and compared with that obtained by FT-IR spectroscopy, and the predicted vibration assignments are made according to the potential energy distribution (PED). The chemical shifts of 1H and 13C-NMR were calculated using the GIAO approximation and compared to experimental values. Using the TD-DFT method, the theoretical UV-Vis absorption spectrum was calculated in chloroform solvent to obtain the most important electronic transitions. Frontier molecular orbitals (HOMO and LUMO) indicate the charge transfer within the molecule. The global chemical reactivity descriptors (GCRD) were calculated. In addition, the MEP was also computed showing the functional groups responsible for building interactions with other molecules. Finally, the nonlinear optical behavior was investigated by the determination of the dipole moment (μ), the polarizability (α), and the first and second hyperpolarizabilities using the same level of theory. All of these findings suggest that the NTDZ crystal may be a viable candidate for NLO applications. Highlights New 1,3,4-thiadiazol derivative was synthesized. X-ray geometry was determined and confirmed by theoretical calculation. Electronic behavior was investigated by DFT and TD-DFT. NLO properties of the compound were also computed.

Ultralow-Power Vertical Transistors for Multilevel Decoding Modes.

Organic field-effect transistors with parallel transmission and learning functions are of interest in the development of brain-inspired neuromorphic computing. However, the poor performance and high power consumption are the two main issues limiting their practical applications. Herein, an ultralow-power vertical transistor is demonstrated based on transition-metal carbides/nitrides (MXene) and organic single crystal. The transistor exhibits a high JON of 16.6mA cm-2 and a high JON /JOFF ratio of 9.12 × 105 under an ultralow working voltage of -1mV. Furthermore, it can successfully simulate the functions of biological synapse under electrical modulation along with consuming only 8.7 aJ of power per spike. It also permits multilevel information decoding modes with a significant gap between the readable time of professionals and nonprofessionals, producing a high signal-to-noise ratio up to 114.15dB. This work encourages the use of vertical transistors and organic single crystal in decoding information and advances the development of low-power neuromorphic systems.

Efficient narrow-band red-light-emitting diodes based on ambipolar organic single crystals

Organic single crystals have attracted immense attention in the field of organic light-emitting devices (OLEDs), owing to their unique advantages of long-range molecular ordering, high carrier mobility, high fluorescent quantum yield and low impurity content. Development of high-performance organic single crystal-based OLEDs with narrow-band emission is critical for high-purity displaying, yet it is still a major challenge to obtain a crystal-based OLED with both narrow fullwidth at half maximum (FWHM) and high electroluminescence (EL) performance. Here, molecular doping engineering is employed by taking 2,6-diphenylanthracene (DPA) as host crystal and pentacene (Pen) as red guest emitter material. 2,2′-Bis[4-(trifluoromethyl)phenyl]-5,5′-bithiazole (BTPB) with strong electron-withdrawing ability are further doped for the growth of ambipolar crystals in order for balanced hole and electron mobility. As a result, DPA: 3% Pen: 15% BTPB crystal-based OLEDs exhibit a maximum luminance and current efficiency of 10,850 cd m −2 and 2.3 cd A −1 , respectively, and an EQE of 1.95%. The obtained red-light-emission with a narrow FWHM increases high color purity of crystal-based OLEDs. It demonstrates that high-performance crystal-based OLEDs with narrow-band emission are of great significance for the development of organic electronics, especially for display and lighting applications. Molecular doping engineering is employed by taking DPA single crystals as host matrix and pentacene as red guest emitter. BTPB with strong electron-withdrawing ability is further doped for obtaining ambipolar crystals. DPA: 3% Pen: 15% BTPB crystal-based OLEDs exhibit a red-light-emission with a narrow FWHM and high-efficiency, which are of great significance for the development of organic single crystal-based electronics. • Doping of pentacene into host DPA crystal enable narrow-band red-light-emission. • Ambipolar crystals obtained by doping N -type BTPB for balanced charge mobility. • Narrow-band EL emission from crystal-based OLEDs increases a high purity. • DPA: 3% Pe: 15% BTPB crystal-based OLEDs exhibit the highest EL performance.

Nonclassical Growth of Atomically Flat Two‐Dimensional Organic Single Crystals on a Liquid Surface through Fusion

AbstractOrganic single crystals with low defect density are key functional materials for next‐generation electronics. Classical crystallization commonly results in a high density of molecular steps, which are defects that can trap charge carriers and reduce the mobility of organic semiconductors. Herein, a novel nonclassical crystallization mechanism involving nucleation, fusion, and growth is designed. The introduction of the fusion stage changes the crystal growth mode from three‐dimensional island growth to two‐dimensional layer‐by‐layer growth and leads to large‐area two‐dimensional molecular crystals with almost no molecular steps. Therefore, the average mobility is observed to improve from 1.26 to 2.07 cm2 V−1 s−1. The nonclassical crystallization mechanism paves the way for atomically flat single crystals to probe the intrinsic optoelectronic properties of organic semiconductors.

Impact of surface free energy on two-dimensional crystallization

Two-dimensional (2D) molecular crystals are emerging materials with fascinating optoelectronic properties. However, growing 2D organic single crystals is challenging because little is known about the factors that determine 2D crystallization. Herein, we investigated the relationship between 2D crystallization and the surface free energy of organic semiconductors. We proposed a term called surface free energy anisotropy factor (g) to measure the tendency of 2D crystallization. Taking two [1]benzothieno[3,2-b][1]benzothiophene derivatives as examples, we identified that the one with a larger g factor showed a higher tendency for 2D crystallization, irrespective of the external factors. This work provides a guideline for the rational design of organic semiconductors toward 2D crystallization.

Studies on structural and third order nonlinear optical properties of bulk size DAST: an interesting organic single crystal for photonic applications

Studies on structural and third order nonlinear optical properties of bulk size DAST: an interesting organic single crystal for photonic applications

Molecular Logic Operations Using Multistimuli Responsive, Mechanically Tunable Elastic Organic Single Crystals

Molecular Logic Operations Using Multistimuli Responsive, Mechanically Tunable Elastic Organic Single Crystals

Direction dependent crystalline perfection, Z-scan studies and fabrication of Type-I and Type-II SHG elements using imidazolium L-tartrate crystals for optical modulator applications

Monoclinic phase (P21) imidazolium l-tartrate (IMLT) has received considerable research interest because of its wide transparency range, good SHG efficiency and phase matchable non-linear optical (NLO) materials. Organic single crystals of IMLT have been grown via a slow cooling method. The grown crystals were oriented using powder X-ray diffraction. The quality of the grown crystals was evaluated using HRXRD studies. Polarized Raman spectroscopy was carried out on b-cut and c-cut IMLT wafers. The third order NLO characteristics of the <1 0 0>, <0 1 0> and <0 0 1> orientated IMLT crystals have been studied using Z-scan measurements with a Hi-Ne laser (632.8 nm). The second-harmonic generation (SHG) intensity was measured for the powdered grown crystals with various particle sizes to explore the second order NLO properties and phase matchability in the crystals. Furthermore, the type-I and type-II phase-matching angle of the XY and XZ (θ <Ω) planes were calculated.

Experimental and theoretical investigation of novel organic L-Glutaminium Benzenesulfonate single crystal – DFT and experimental approach

An organic nonlinear optical crystal of l-Glutaminium Benzenesulfonate (LGBS) crystal was grown by slow evaporation method. Crystallization parameters and structural analysis of LGBS crystal were notified by Single crystal XRD technique and the theoretical structural parameters were also identified and compared using DFT. The grown LGBS crystal crystallizes in monoclinic crystal system with the non-centrosymmetric space group P21. The presence of chemical bonding and functional groups were examined using FTIR and FT Raman spectra and their theoretical assignments were calculated. The lower cutoff wavelength was determined for grown LGBS crystal by UV–visible spectroscopy and it confirms that grown LGBS crystal has wide transmittance in the visible region. The emission region for the grown LGBS crystal was analysed by fluorescence spectrum. The global reactive descriptors and the intermolecular charge transfer interactions were also interpreted. The liberation of organic molecule and melting temperature of LGBS crystal were elucidated by thermo gravimetric analysis (TG) and DSC. The Kurtz and Perry powder technique confirms the formed LGBS crystal exhibits the second harmonic generation (SHG) and its outputs were compared with standard KDP.

'Molecular Beam Epitaxy' on Organic Semiconductor Single Crystals: Characterization of Well-Defined Molecular Interfaces by Synchrotron Radiation X-ray Diffraction Techniques.

Epitaxial growth, often termed “epitaxy”, is one of the most essential techniques underpinning semiconductor electronics, because crystallinities of the materials seriously dominate operation efficiencies of the electronic devices such as power gain/consumption, response speed, heat loss, and so on. In contrast to already well-established epitaxial growth methodologies for inorganic (covalent or ionic) semiconductors, studies on inter-molecular (van der Waals) epitaxy for organic semiconductors is still in the initial stage. In the present review paper, we briefly summarize recent works on the epitaxial inter-molecular junctions built on organic semiconductor single-crystal surfaces, particularly on single crystals of pentacene and rubrene. Experimental methodologies applicable for the determination of crystal structures of such organic single-crystal-based molecular junctions are also illustrated.

Organic Semiconductor Single‐Crystal Light‐Emitting Transistors

AbstractOrganic semiconductor single crystals, with the unique advantages of high carrier transport properties, high optical quality, and low defect density, are ideal candidates for constructing high‐performance organic light‐emitting transistors (OLETs) and advancing their related potential applications, including smart displays, micro‐nano light sources, organic electrically pumped lasers, and integrated photonic circuits. Recently, significant progress has been made in organic semiconductor single‐crystal light‐emitting transistors (OSSCLETs), particularly high‐mobility emissive organic semiconductor single crystals, high‐performance light‐emitting transistors, and color‐tunable organic semiconductor single crystals and OLETs. In this review, the exciting advances in OSSCLETs are summarized in terms of advanced organic semiconductor materials, high‐quality organic semiconductor single crystals, advanced device technologies, and high‐performance light‐emitting transistors. Finally, the challenges and prospects of OSSCLETs as well as promising research directions in this field are briefly summarized.