Organic Single Crystals Research Articles

Modulating contact properties by molecular layers in organic thin‐film transistors

AbstractAdvanced organic devices and circuits demand both ultrahigh charge carrier mobilities and ultralow‐resistance contacts. However, due to a larger access resistance in staggered organic thin‐film transistors (OTFTs), the achievement of ultralow contact resistance () is still a challenge. The modulation of contact resistance by molecular layers near the interface has been rarely reported. Here, we demonstrate that few‐layer organic single crystals are grown on hafnium oxide (HfO2) by solution‐shearing epitaxy. We utilize these organic crystals to fabricate bottom‐gate staggered OTFTs with different contact processes. The results show that the contact properties of OTFTs are obviously modulated by crystal layers. The tri‐layer (3L) evaporated‐Au C10‐DNTT OTFTs exhibit optimal electrical performance, including ultralow of 5.6 Ω ∙ cm, recorded transfer length of 0.4 μm, field‐effect mobility over 14 , threshold voltage lower than 0.3 V, and long‐term air stability over 8 months. The main cause is that the metal atoms can penetrate into the charge transport layer, with damage‐free, in 3L evaporated‐Au OTFTs; nevertheless, it cannot be realized in other cases. Due to layer stacking of conjugated molecules and polymers, our strategy can efficiently modulate the contact resistance to aid the development of high‐performance organic devices and circuits.

Growth and characterization of organic 4-hydroxybenzophenone single crystals for nonlinear optical applications

Growth and characterization of organic 4-hydroxybenzophenone single crystals for nonlinear optical applications

Thickness control of organic semiconductor-incorporated perovskites.

Two-dimensional organic semiconductor-incorporated perovskites are a promising family of hybrid materials for optoelectronic applications, owing in part to their inherent quantum well architecture. Tuning their structures and properties for specific properties, however, has remained challenging. Here we report a general method to tune the dimensionality of phase-pure organic semiconductor-incorporated perovskite single crystals during their synthesis, by judicious choice of solvent. The length of the conjugated semiconducting organic cations and the dimensionality (n value) of the inorganic layers can be manipulated at the same time. The energy band offsets and exciton dynamics at the organic-inorganic interfaces can therefore be precisely controlled. Furthermore, we show that longer and more planar π-conjugated organic cations induce a more rigid inorganic crystal lattice, which leads to suppressed exciton-phonon interactions and better optoelectronic properties as compared to conventional two-dimensional perovskites. As a demonstration, optically driven lasing behaviour with substantially lower lasing thresholds was realized.

Deformation-induced phosphorescence shift in a 2D elastically flexible organic single crystal: role of chalcogen-centered weak interactions

Deformation-induced phosphorescence shift in a 2D elastically flexible organic single crystal: role of chalcogen-centered weak interactions

Synthesis, Structural, Spectroscopic and Quantum Chemical Investigation of a Novel 1,4-Diamino-2,5-dichlorobenzenium Picrate Single Crystal: An Efficient NLO Material

A new organic nonlinear optical single crystal, 1,4-diamino-2,5-dichlorobenzenium picrate (DADCBP) has been successfully grown by solvent slow evaporation method. DADCBP crystallizes in a triclinic structure with the centrosymmetric space setup, P-1. The molecular structure of the grown crystal has been determined by NMR spectral analysis. The existence of discrete functional branches of the crystal has been identified by FTIR spectral study. The optical property of the title crystal has been measured by UV-Vis-NIR spectral analysis. PL spectra reveal the emission bands of the grown crystal. The thermal stability of the harvested crystal has been examined by the TG/DTA study. The dielectric constant and loss have been taken to locate the arrangement of charges in the grown crystal. The quantum chemical studies have been performed to analyze the HOMO/LUMO, molecular geometry, and mulliken atomic charge by B3LYP at the 6-311++G (d,p) level of theory. H···H, O···H, C···H, C···C various intermolecular interactions of hydrogen bonds in the DADCBP molecule have been visualized by the Hirshfeld surface analysis. The nonlinear optical (NLO) characteristics like nonlinear absorption coefficient (β), nonlinear refractive index (n2) and susceptibility (χ(3)) have been examined using the Z-scan technique.

Wafer-Scale Epitaxial Growth of Two-dimensional Organic Semiconductor Single Crystals toward High-Performance Transistors.

The success of state-of-the-art electronics and optoelectronics relies heavily on the capability to fabricate semiconductor single-crystal wafers. However, the conventional epitaxial growth strategy for inorganic wafers is invalid for growing organic semiconductor single crystals due to the lack of lattice-matched epitaxial substrates and intricate nucleation behaviors, severely impeding the advancement of organic single-crystal electronics. Here, an anchored crystal-seed epitaxial growth method for wafer-scale growth of 2D organic semiconductor single crystals is developed for the first time. The crystal seed is firmly anchored on the viscous liquid surface, ensuring the steady epitaxial growth of organic single crystals from the crystal seed. The atomically flat liquid surface effectively eliminates the disturbance from substrate defects and greatly enhances the 2D growth of organic crystals. Using this approach, a wafer-scale few-layer bis(triethylsilythynyl)-anthradithphene (Dif-TES-ADT) single crystal is formed, yielding a breakthrough for organic field-effect transistors with a high reliable mobility up to 8.6 cm2 V-1 s-1 and an ultralow mobility variable coefficient of 8.9%. This work opens a new avenue to fabricate organic single-crystal wafers for high-performance organic electronics.

An elastic luminescent organic single crystal with linear and nonlinear optical waveguide properties

In recent years, organic single crystals combining elastic and photoluminescent (PL) properties have attracted extensive attention due to their promising applications in many fields. However, elastic organic crystals with two-photon luminescence (2 PL) waveguiding properties are still rarely found, which is imperative for various applications, including near-infrared (NIR) bioimaging and nonlinear optical (NLO) photonic devices. This work reports an elastic single crystal with a long needle shape, anthracene-9,10-dicarbaldehyde (An-DC). Its crystal (100) face exhibits highly reversible bending by applying the mechanical force, which is facilitated by the van der Waals (C– H···π), H-bond (C–H⋯O), and π···π interactions among molecules. The crystal emits a strong orange-red fluorescence when excited by blue-violet light. Interestingly, it also exhibits excellent two-photon fluorescence emission when stimulated by near-infrared light. Based on these linear and nonlinear optical characteristics, the waveguide applications of the An-DC crystal were implemented. Notably, in the bending state, the luminescence performance and the crystal structure of the An-DC crystal are maintained well, which can be used as a low-loss material for linear and nonlinear optical waveguide devices, thus expanding the potential use of flexible organic crystals.

Exploring the potential of l-glutamic acid hydrochloride: growth, characterization, and applications in organic nonlinear optical single crystals for optoelectronic and photonic devices

Exploring the potential of l-glutamic acid hydrochloride: growth, characterization, and applications in organic nonlinear optical single crystals for optoelectronic and photonic devices

A comparative study of structural and spectroscopic properties of three structurally similar mechanically bending organic single crystals – 2-Amino-3-nitro-5-halo (halo = Cl, Br, or I) pyridine

In recent years, scientists have been very interested in single crystals of monoaromatic compounds with mechanical softness, but they are hard to find. The present work reports a comparative study of structural, spectroscopic, and quantum chemical investigations of three structurally similar mechanically bending monoaromatic compounds, namely, 2-amino-3-nitro-5-chloro pyridine (I), 2-amino-3-nitro-5-bromo pyridine (II), and 2-amino-3-nitro-5-iodo pyridine (III). The mechanical responses of the three organic crystals studied here are very intriguing due to the similarity of their chemical structures, which only differ in the presence of halogen atoms (Cl, Br, and I) at the fifth position of the pyridine ring and are explained through examining intermolecular interaction energies from energy frameworks analysis, slip layer topology, and Hirshfeld surface analysis. The crystals of all the three feature one dimensional ribbons comprising alternating NaminoH⋯Onitro and NaminoH⋯Npyridine hydrogen bonds that form R22(12) and R22(8) dimeric rings, respectively. In (III), weak I⋯I interactions link the adjacent ribbons forming a two dimensional sheet. Layer-like structures are observed in all three crystals, with no significant interactions between the adjacent architectures (ribbons or sheets). Energy framework calculations are used for estimating the bending ability of the three compounds, with the three following the order Cl ≪ Br < I. The iterative electrostatic scheme coupled with the supermolecule approach (SM) at the DFT/CAM-B3LYP/aug-cc-pVTZ level is used to calculate the third-order nonlinear susceptibility (χ3) values in a simulated crystalline environment for the static case as well as two typical electric field frequency values, (λ = 1064 nm) and (λ = 532 nm). In addition, estimates of the topological studies (localized orbital locator and electron localization function) and reactivity characteristics (global reactivity parameters, molecular electrostatic potential, and Fukui function) are made for the compounds under investigation. Docking studies done using AutoDock software with a protein target (PDB ID: 6CM4) revealed that three compounds could be used to treat Alzheimer's disease.

Investigation on growth, crystal structure, third-order optical nonlinearity properties and DFT computational studies of novel proton transfer 3-aminopyridine P-nitrobenzoate P-nitrobenzoic acid (3APPNB) single crystal for third-order NLO applications

A new organic single crystal of 3-aminopyridine p-nitrobenzoate p-nitrobenzoic acid (3APPNB) with a size of 8 × 4 × 2 mm3 was grown by slow evaporation solution growth technique at room temperature using methanol solvent. The lattice parameter values were evaluated with the help of single crystal XRD and it confirms that the 3APPNB crystal belongs to triclinic crystal structure and the space group P-1. Crystal unit cell parameters are a = 9.3384(5) Å, b = 10.0403(5) Å, c = 11.094(6) Å, α = 109.4940(10)°, β = 93.964(2)°, γ = 99.890(2)° and V = 957.03 (9) (Å3) were determined. The 3APPNB crystal crystallizes in a centrosymmetric nature, triclinic system and space group P-1. SCXRD study shows that both the anion and the cation are interlinked to each other by two types of symmetrical intermolecular C–H…O and N–H···O hydrogen bonds. The crystalline nature and hkl phases have been determined using Powder XRD studies. The presence of different vibrational groups in the 3APPNB compound is examined by employing Fourier transform infrared (FT-IR) spectral analysis. UV–Vis-DRS spectral analysis signifies that the 3APPNB has a wide transmittance (98 %) and a cut-off wavelength of around 317 nm. The etch pit density (EDP) of 3APPNB crystal was examined by a chemical etching analysis. The thermal studies expose that 3APPNB is thermally stable up to 172 °C. The surface morphology of the 3APPNB is analyzed by SEM. The nonlinear properties like β, n2 and χ(3) were measured through the Z-scan analysis and the values were calculated to be 5.78 × 10−5 m/W, 8.05 × 10−12 m2/W) and χ(3) = 8.936 × 10−9. The third-order nonlinear optical (TONLO) χ(3) values are higher. The achieved TONLO χ(3) value when compared to other similar constituents is owing to the tarnish movement of π-electron configuration from the donor to an acceptor that makes the molecules highly polarized. The results reveal that the 3APPNB crystal finds applications in devices like optical switching and optical limiting. The quantum-chemical theoretical analyses are performed to measure the intrinsic properties of the 3APPNB molecules using DFT calculation. The band gap, orbital energy and second hyperpolarizability are also studied using changing the applied field. Furthermore, Quantum chemical calculations are used to obtain the MESP, HOMO-LUMO and first-order hyperpolarizability for the 3APPNB compound.

General Spatial Confinement Recrystallization Method for Rapid Preparation of Thickness-Controllable and Uniform Organic Semiconductor Single Crystals.

Organic semiconductor single crystals (OSSCs) are ideal materials for studying the intrinsic properties of organic semiconductors (OSCs) and constructing high-performance organic field-effect transistors (OFETs). However, there is no general method to rapidly prepare thickness-controllable and uniform single crystals for various OSCs. Here, inspired by the recrystallization (a spontaneous morphological instability phenomenon) of polycrystalline films, a spatial confinement recrystallization (SCR) method is developed to rapidly (even at several second timescales) grow thickness-controllable and uniform OSSCs in a well-controlled way by applying longitudinal pressure to tailor the growth direction of grains in OSCs polycrystalline films. The relationship between growth parameters including the growth time, temperature, longitudinal pressure, and thickness is comprehensively investigated. Remarkably, this method is applicable for various OSCs including insoluble and soluble small molecules and polymers, and can realize the high-quality crystal array growth. The corresponding 50 dinaphtho[2,3-b:2″,3″-f]thieno[3,2-b]thiophene (DNTT) single crystals coplanar OFETs prepared by the same batch have the mobility of 4.1 ± 0.4 cm2 V-1 s-1 , showing excellent uniformity. The overall performance of the method is superior to the reported methods in term of growth rate, generality, thickness controllability, and uniformity, indicating its broad application prospects in organic electronic and optoelectronic devices.

Laser-induced crystallization of fluoranthene in both vapor and solution media

Organic single crystals are attracting enormous attention and playing an indispensable role in the realization of high-performance electronic devices. In this paper, we reported an in situ growth method for two-dimensional branch-like and hexagonal shapes of fluoranthene crystals under the photophoretic and dielectrophoretic forces generated by the photothermal and photovoltaic effects in both vapor- and liquid- environments. The crystals grown via this method are characterized by real-time controllability and large size. At the same time, the crystal morphology can also be modified through non-contact illumination. This growth method may serve the future demand for crystal growth in different phases.

Hollow Mesoporous Metal Organic Framework Single Crystals Enabled by Growth Kinetics Control for Enhanced Photocatalysis

AbstractThe tailored design of hollow mesoporous metal−organic framework (MOF) single crystals to realize the unimpeded mass transport and long‐range carrier migration for advanced photoelectric applications is attractive while being a major challenge. Here, a kinetically mediated micelle assembly strategy is presented to synthesize hollow UiO‐66(Ce) single crystals in 1,3,5‐trimethylbenzene (TMB)‐H2O emulsion system with Pluronic F127/P123 as dual surfactants. This synthesis features the employment of modulator acetic acid, which can coordinate growth kinetics of MOFs, allowing the nucleation of MOF on block polymer micelles and transforming the self‐assembly of block polymer/MOF composite monomicelles from water to TMB/H2O emulsion interface and the growth of MOF from aggregation to oriented attachment, and thus ensuring the formation of hollow mesoporous UiO‐66(Ce) single crystals. Moreover, a precise control in cavity diameter from ≈0 to ≈600 nm, mesopore structure from close to radial and dendritic can be achieved by tuning the amount of TMB and the ratio of F127/P123. As a result, the hollow mesoporous UiO‐66(Ce) single crystals with large radial mesopores (≈25 nm) and high surface area (≈1061 m2 g) exhibit excellent photocatalytic performance for H2 generation owing to enhanced permeability and suppressed electron‐hole combination.

Investigation of nonlinear absorption coefficient (β) and nonlinear refraction (n2) of L-threoninium P-toluenesulfonate monohydrate organic single crystal using two laser sources

Third order nonlinear optical properties of organic crystal L-threoninium P-toluenesulfonate monohydrate was investigated by ‘Z-scan’ technique employing two different laser sources under different intensities at 532 nm CW laser and 1064 nm pulsed laser respectively. Nonlinear absorption coefficient (αNL) and nonlinear refraction (n2) were evaluated at six different intensities using 532 nm CW laser source and with pulsed laser source (λ = 1064 nm) by changing the pulse rate keeping intensity same. It is found that this crystal possesses positive nonlinearity and exhibit saturation absorption.

Improving Charge Injection for Organic Field‐Effect Transistor Array via Chemical Functionalized Van der Waals Top‐Contacts

AbstractEfficient charge injection at metal/semiconductor interface is of great importance for high‐performance organic field‐effect transistors (OFETs). In OFETs, top‐contact configuration generally exhibits better injection efficiency but may induces thermal damage to organic layer and is intrinsically difficult to modified with chemisorbs at metal/semiconductor interface. Herein, a versatile, large‐scale and damage‐free metal integration strategy is reported to achieve efficient charge injection in OFETs by applying self‐assembly monolayers (SAMs) functionalized van der Waals (vdW) top‐contact electrodes. Centimeter scale metal electrodes are transferred onto organic single crystal to form OFETs array without residual left. vdW contact provides a clear and atomic sharp interface, and thus the inherent electronic structure and physical properties of the pristine heterostructure interface can be retained. Modifying fluorinated SAMs at metal/semiconductor interface alters the work function of Au by 350 meV, and thus reduces the energy barrier for charge injection. As a result, OFETs array exhibits excellent performance characteristics with an average mobility of 3.6 cm2 V−1 s−1, negligible hysteresis and a high on/off ratio above 106 on high‐k AlOx dielectric. Organic unipolar inverters based on all vdW contact are also demonstrated. This strategy paves the way for both fundamental study and practical applications of organic electronics.

Tosylate family crystals for optoelectronic applications

Since the discovery of lasers, high-quality nonlinear optical (NLO) single crystals have served as the foundation for the creation of novel, cutting-edge devices that meet societal demands. Modern optoelectronic applications such as telecommunication lasers, optical fibers, photodiodes, solar cells, etc. favor high-performance nonlinear optical single crystals with improved optical nonlinearity. Organic crystals are extensively explored for these applications because of their high NLO coefficient. This paper deals with the problems and advancements of organic nonlinear optical single crystals. Here, we review the growth and characterizations of various tosylate family crystals from the vast realm of organic single crystals and their potential applications in the field of optoelectronic devices. Various properties like linear and nonlinear optical, thermal, mechanical, and laser damage threshold values for these samples have been summarized. The attempts are made for highlighting how these tosylate (p-Toluenesulfonic acid based) family crystals can be realized into efficient optoelectronic devices by summarizing variously reported cut-off wavelengths and their wide transmission ranges.

Growth and characterization of Oxalic acid doped Guanidine carbonate (OGC) single crystal

Oxalic acid doped Guanidine carbonate, an organic nonlinear optical single crystal is developed successfully by slow evaporation solution growth method using deionized water as a solvent. The crystal structure and lattice parameters of grown crystals are determined by single crystal X – ray diffraction of the grown crystal. The presence of expected functional groups of the grown crystal is identified by Fourier Transform Infrared spectroscopy. The optical transmittance spectrum of the crystals has been recorded by UV –Vis-NIR spectral analysis. The calculated large bandgap of the grown crystals attests them for optoelectronic applications. The Thermo Gravimetric and Differential Thermal analyses have been carried out to understand the thermal responses of the crystals. Second harmonic generation efficiency of the grown crystals have been calculated by Kurtz powder method. Nd – YAG laser (1064 nm) was used to find out the laser damage threshold of the grown crystal. The inspiring results confirms that the grown crystal serve as a potential candidate for photonic devices.

Highly Efficient Inherent Linearly Polarized Electroluminescence from Small-Molecule Organic Single Crystals.

Small-molecule organic single crystals (SCs) with an inherent in-plane anisotropic nature enable direct linearly polarized light emission without the need for spatially separated polarizers and complex optical structures. However, the device performance is severely restricted by the starvation of appropriate SC emitters and the difficulty in the construction of efficient SC electroluminescence (EL) devices, leading to a low external quantum efficiency (EQE) of usually smaller than 1.5%. Here, highly efficient inherent linearly polarized light-emitting diodes (LP-LEDs) are demonstrated by exploiting 2,6-diphenylanthracene (DPA) SCs as intrinsically polarized emitters. The LP-LEDs exhibit a 2.5-fold enhanced maximum EQE of 3.38%, which approaches the theoretical limit for the DPA SC-based EL device and is the highest among organic SC-based LEDs reported thus far. More importantly, a high degree of polarization (DOP) up to 0.74 is achieved for the intrinsically polarized EL emission of the DPA SC-based LP-LEDs. By leveraging the highly efficient LP-LED, an interchip polarized optical communication system consisting of organic SCs is demonstrated for the first time. This work creates a solid foundation for the exploitation of a vast new library of small-molecule organic SCs for LP-LEDs and carries broad implications for polarized optics and relevant optoelectronic devices.

An organic (4-nitrophenyl) methionine single crystal: growth, optical properties and quantum chemical investigations for NLO device fabrication

An organic (4-nitrophenyl) methionine single crystal: growth, optical properties and quantum chemical investigations for NLO device fabrication

Vapor-Induced Coating Method for Well-Aligned and Uniform Organic Semiconductor Single Crystals

Vapor-Induced Coating Method for Well-Aligned and Uniform Organic Semiconductor Single Crystals