Organic Heterostructures Research Articles

MAPLE-Deposited Perylene Diimide Derivative Based Layers for Optoelectronic Applications.

Nowadays, the development of devices based on organic materials is an interesting research challenge. The performance of such devices is strongly influenced by material selection, material properties, design, and the manufacturing process. Usually, buckminsterfullerene (C60) is employed as electron transport material in organic photovoltaic (OPV) devices due to its high mobility. However, considering its low solubility, there have been many attempts to replace it with more soluble non-fullerene compounds. In this study, bulk heterojunction thin films with various compositions of zinc phthalocyanine (ZnPc), a perylene diimide derivative, or C60 were prepared by matrix-assisted pulsed laser evaporation (MAPLE) technique to assess the influence of C60 replacement on fabricated heterostructure properties. The investigations revealed that the optical features and the electrical parameters of the organic heterostructures based on this perylene diimide derivative used as an organic acceptor were improved. An increase in the JSC value (4.3 × 10-4 A/cm2) was obtained for the structures where the perylene diimide derivative acceptor entirely replaced C60 compared to the JSC value (7.5 × 10-8 A/cm2) for the heterostructure fabricated only with fullerene. These results are encouraging, demonstrating the potential of non-fullerene compounds as electron transport material in OPV devices.

Construction of COF/COF Organic S-Scheme Heterostructure for Enhanced Overall Water Splitting.

Covalent organic frameworks (COFs) as a new type of photocatalysts have shown unique advantages in visible-light-driven hydrogen evolution, while the reported overall water-splitting systems are still very rare among various COF-based photocatalysts. Herein, two COFs are integrated to construct a type of organic S-scheme heterojunction for improved overall water splitting. In this system, TpBpy-COF and COF-316 serve as H2- and O2-evolving components, respectively, which are combined through π-π interaction between conjugated aromatic rings. By introducing ultra-small Pt nanoparticles (NPs) into the pores of the TpBpy-COF nanosheets (NS), the resultant COF-316/Pt@TpBpy-COF NS heterostructure achieves extremely high H2 and O2 evolution rates of 220.4 and 110.2µmolg-1h-1, respectively, under visible light irradiation (λ ≥ 420nm). The results of transient absorption spectra (TAS) and photoelectronic measurements indicate that the organic heterojunction interface notably facilitates the separation and transfer of photogenerated electron-hole pairs. Further, theoretical calculations and in situ experiments confirm the spontaneous formation of the COF/COF heterojunction interface and the active sites for overall water splitting.

Facile interface engineering of highly stable covalently functionalized graphene oxide-nickel based metal organic framework heterostructures for supercapacitor applications

This study presents the synthesis, characterization and electrochemical studies of the covalently connected 2D/2D heterostructures of nickel-based metal-organic framework (Ni-MOF)/graphene oxide (GO) hybrids. The covalent linkage in GO plays a vital role in the growth of Ni-MOF onto the functionalized GO and these hybrids (NG) show fascinating structural properties. An appreciable reduction of GO is observed in NG hybrids with an increase in Ni-MOF concentration. The NG hybrids display exceptional structural stability with a maximum of 96 % capacitance retention even after 10,000 cycles and augmented electrochemical performance (151.8 F g-1 at a current density of 0.5 A g-1).

Directional self-assembly of organic vertically superposed nanowires

Organic crystal-based superimposed heterostructures with inherent multichannel characteristics demonstrate superior potential for manipulating excitons/photons at the micro/nanoscale for integrated optoelectronics. However, the precise construction of organic superimposed heterostructures with fixed superimposed sites remains challenging because of the random molecular nucleation process. Here, organic vertically superimposed heterostructures (OSHs) with fixed superimposed positions are constructed via semi-wrapped core/shell heterostructures with partially exposed cores, which provide preferential nucleation sites for further molecular epitaxial growth processes. Furthermore, the relative length ratio from 21.7% to 95.3% between interlayers is accurately adjusted by regulating the exposed area of the semi-wrapped core/shell heterostructures. Significantly, these OSHs with anisotropic optical characteristics demonstrate well regulation of excitation position-dependent waveguide behaviors and can function as photonic barcodes for information encryption. This strategy provides a facile approach for controlling the nucleation sites for the controllable preparation of organic heterostructures and advanced applications for integrated optoelectronics.

Epitaxial Growth of Two-Dimensional Organic Crystals with In-Plane Heterostructured Domain Regulation.

Complex organic lateral heterostructures (OLHs) with spatial distribution of two or more chemical components are crucial for designing and realizing unique structure-dependent optoelectronic applications. However, the precise design of well-defined OLHs with flexible domain regulation remains a considerable challenge. Herein, we present a stepwise solution self-assembly method to synthesize two-dimensional (2D) OLHs with a central rhombus domain and a lateral region featuring tunable blue and green emission based on the sequential nucleation and growth of 2D crystals. By controlling the initial crystallization time of 2,6-diphenylanthracene, the rhombic length ratio (α) of the multicolor-emissive part of the 2D OLHs is precisely modified. Furthermore, a third lateral layer is constructed on the resulting OLHs, demonstrating scalable lateral regulation. Significantly, these prepared 2D OLHs exhibit great excitation position-dependent waveguide characteristics and enable a 0.06 dB/μm low-loss waveguiding, which are conducive to photon transport and conversion for photonic integrated circuits. This work provides a stepwise strategy for the accurate fabrication of 2D OLHs, fabricating the developments of next-generation optoelectronics devices.

Organic Heterostructures with Dendrimer Based Mixed Layer for Electronic Applications.

Recently, much research has focused on the search for new mixed donor-acceptor layers for applications in organic electronics. Organic heterostructures with layers based on the generation 1 poly(propylene thiophenoimine) (G1PPT) dendrimer, N,N'-diisopropylnaphthalene diimide (MNDI), and a combination of the two were prepared and their electrical properties were investigated. Single layers of G1PPT and MNDI and a mixed layer (G1PPT:MNDI) were obtained via spin coating on quartz glass, silicon, and glass/ITO substrates, using chloroform as a solvent. The absorption mechanism was investigated, the degree of disorder was estimated, and the emission properties of the layers were highlighted using spectroscopic methods (UV-Vis transmission and photoluminescence). The effects of the concentration and surface topographical particularities on the properties of the layers were analyzed via atomic force microscopy. All of the heterostructures realized with ITO and Au electrodes showed good conduction, with currents of the order of mA. Additionally, the heterostructure with a mixed layer exhibited asymmetry in the current-voltage curve between forward and reverse polarization in the lower range of the applied voltages, which was more significant at increased concentrations and could be correlated with rectifier diode behavior. Consequently, the mixed-layer generation 1 poly(propylene thiophenoimine) dendrimer with N,N'-diisopropylnaphthalene diimide can be considered promising for electronic applications.

Programmable In-Situ Co-Assembly of Organic Multi-Block Nanowires for Cascade Optical Waveguides.

Organic heterostructures (OHs) with multi-segments exhibit special optoelectronic properties compared with monomeric structures. Nevertheless, the synthesis of multi-block heterostructures remains challenging due to compatibility issues between segment parts, which restricts their application in optical waveguides and integrated optics. Herein, we demonstrate programmable in-situ co-assembly engineering, combining multi-step spontaneous self-assembly processes to promote the synthesis of multi-block heterostructures with a rational arrangement of three or more segments. The rational design of segments enables exciton manipulation and ensures optical waveguides and proper output among the multi-segment OHs. This work enables the controllable growth of segments within multi-block OHs, providing a pathway to construct complex OHs for the rational development of future optical applications.

Optically enhanced organic phototransistors for adaptive image processing under complex light conditions

Effectively handling massive information in complex lighting conditions is crucial for security-focused machine vision, as it relies on precise image feature detection and encryption/decryption to ensure integrity and confidentiality. Traditional hardware, primarily based on complementary metal-oxide-semiconductor (CMOS) technology, struggles with the complexity of processing tasks around the clock. To address this challenge, a ternary organic heterostructure visuomorphic phototransistor was tailored for adaptive critical image processing. The light coupling induced by the porous heterostructural layer enhances the light absorption efficiency by 2.5-fold. Our phototransistor exhibits bidirectional photoresponse across the visible and near-infrared (NIR) spectral regions, enabling adaptive edge detection in varying lighting conditions with precision above 85 %. The phototransistor array facilitates image encryption/decryption with a superior accuracy of 12 %/90 % compared to existing counterparts. This ternary organic hetero-integration combines multiple response modes, enabling compact and efficient critical feature processing.

Highly sensitive volatile organic compounds monitoring enabling by silver-nanowire@metal–organic frameworks core-shell heterostructure

Metal–organic frameworks (MOFs) hold great promise as advanced chemical sensing materials due to their high surface area and tunable surface chemistry. However, due to the inherent conductivity, building a highly sensitive MOFs-based gas sensor for real-time monitoring hazardous gas operated at room temperature (RT) is still a huge challenge. Herein, an in-situ anchoring strategy is proposed to construct a 1D-0D core-shell heterostructure by integrating silver nanowires (AgNWs) with highly conductivity and Zn-MOF with high specific surface area. The incorporation of AgNWs establishes a highly conductive network architecture to facilitate rapid charge transport while preventing the Zn-MOF nanoparticles from agglomeration, ensuring an effective transmission highway for target gas molecules. Meanwhile, the Zn-MOF nanoparticles induce remarkable absorption capacity and contribute high gas response. By strategically amalgamating the inherent distinctive virtues of the individual components and capitalizing on the synergistic benefits arising from the composite, the sensors hinged upon the refined AgNWs@Zn-MOF (A@Z) heterostructure unveiled remarkable response value of 27 to 20 ppm ethanol at RT, accompanied by a low detection limit of 1 ppm. Moreover, the A@Z sensor further showcases superior selectivity and repeatability. This work offers a fresh standpoint for the fabrication of MOF-based heterostructures, fostering advancements in diverse applications.

Electro-photocatalyst effect of N-S-doped carbon dots and covalent organic triazine framework heterostructures for boosting photocatalytic degradation of phenanthrene in water

In the present study, we introduce a covalent organic triazine framework polymer (COTF-P) using 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) with triazine-based amine. The resulting dark red COTF-P illustrated potential behavior as a photocatalyst under visible light. Due to the inadequate solar energy capture and ultrafast charge recombination of the resulting COTF-P, the prepared COTF-P has been decorated with CQDs (N-CQD and N-S-CQD) to build a Z-scheme CQDs/COTF-P heterojunction photocatalyst and utilizes as photocatalyst for the breakdown of phenanthrene (PHE) exposed to visible light. The prepared COTF-P and CQDs/COTF-P were fully characterized, analyzing the textural (N2 isotherms), structural (XRD and FTIR), chemical (EDX and XPS), morphological (FESEM and TEM), optical (DRS-UV-Vis and photoluminescence), and electrochemical properties (EIS impedance, transient photocurrent, and flat band potential). The prepared N-S-CQD/COTF-P heterojunction displayed optimum activity for the photocatalytic oxidation of PHE from water, owing to an enhanced separation of the photogenerated charges and lower bandgap value, 2.1 vs. 1.9 eV. The N-S-CQD/COTF-P heterojunction showed acceptable stability in terms of activity and structural properties after 5 cycles of reuse. The mechanism of activation highlights the importance played by superoxide radicals and hydroxyl radicals. This project sheds light on the potential use of CQDs for the decoration of polymers, extending the absorbance in the visible region and boosting the migration of charge, which boosts the activity of the resulting material.

High‐Performance P‐N Junction Heterostructure with Carbon Quantum Dot and Nitrogen Self‐Doped Graphitic Carbon Nitride for Visible Light Photodetection

AbstractOrganic photodetectors (OPDs) hold immense promise for optoelectronic applications. Here a zero‐biased, high‐performance organic photodetector employing a 2D organic heterostructure is introduced. The structure combines carbon quantum dots (CQDs) with nitrogen self‐doped graphitic carbon nitride (g‐C3N4+) and is tested for alternating current (AC) photodetection on an interdigitated electrode platform. The study reveals extraordinary performance driven by the synergistic effects of efficient charge excitation, separation, and emission within the 2D/2D CQD/g‐C3N4+ heterostructure, leveraging mechanisms of photoconduction, photogating, and fluorescence. A unique convergence to similar rise and decay times in the order of 2.9 ms is observed at higher frequencies in the visible (Vis) spectrum. Benchmarking against state‐of‐the‐art OPDs shows ultrahigh specific detectivity (4.60 × 1018 Jones), ultrahigh responsivity (1.43 × 107 A W−1), high external quantum efficiency (43 × 107%) at an optical intensity of 3.56 × 10−4 mW cm−2 and a wavelength of 405 nm while delivering competitive performance at 532 and 635 nm as well. Moreover, a large linear dynamic range of 86–162 dB in the Vis spectrum is obtained. These enhancements promise development of a new generation of OPDs to advance light sensing and imaging applications at high frequency, marking a significant milestone in optoelectronic device engineering.

Multifunctional application of planar 2D molecule for light-emitting heterostructures

The object of research is the donor-acceptor compound, organic and hybrid heterostructures based on it. The paper is focused on a comprehensive approach to solving the problem of the efficiency of light-emitting devices, finding new technological and design solutions for the use of organic compounds as multifunctional materials for various types of light-emitting devices. The paper presents the multifunctional application of a planar 2D molecule as an emission layer for typical and inverted types of light-emitting heterostructures, as well as a matrix for a host-guest system using inorganic quantum dots. The developed light-emitting structures are characterized by external quantum efficiency typical for fluorescent devices, but good stability over the entire length of the consumption voltage. QLED brightness is 1600 cd·m-2 and EQE 1.4 %, which are good parameters for use in display technology. Organic LEDs based on planar molecules are promising candidates for use in modern lighting systems. A separate advantage of these light-emitting structures is the multifunctionality of using one compound for different types of light-emitting structures, including inverted heterostructures. Special attention is paid to the technological and design implementation of invert structures, since their geometry allows direct connection to the back board of the n-channel transistor on the substrate. In addition, organic LEDs have low energy consumption and are environmentally friendly due to the absence of toxic substances in their architecture, which creates the prerequisites for saving energy resources and reducing the industrial burden on the environment.

Single atom intercalation in 2D triazine-based (g-C6N6) and boroxine-based (B6O6) porous covalent organic framework bilayers and heterostructures

Covalent organic frameworks (COFs) are new class of organic porous materials with tunable pore size and low weight density, demonstrating remarkable potential applications in gas storage, gas separation, and catalysis. The inherent periodic porosity of COF monolayers (MLs) establishes anchoring sites for single atoms. Using first-principles calculations, we study the structural and electronic properties of atom-embedded C6N6 and B6O6 MLs. Subsequently, the intercalation of atoms between C6N6 and B6O6 bilayers (BLs) and their heterostructure (HTS) are investigated. Our findings show the significant effects of embedded atoms on the structural parameters of the host material. Notably, the Li atom anchors within the pore region of C6N6 ML without forming bonds, while it establishes two σ bonds with O atoms in B6O6 ML. The Cs atom forms six bonds in both MLs and resides between layers in BLs. In the HTS, the Cs atom forms six bonds with N atoms of the C6N6 layer, positioning in the middle of the layers. Calculations reveal that Li and Cs atoms induce a red shift in energy, leading to a semiconductor–metal transition. Conversely, the insertion of an F atom induces a blue shift in energy, creating a midgap state at the Fermi energy.

Regulating dynamic growth pathway for constructing organic heterostructures of interchangeable microblocks and adjustable optical output

Regulating dynamic growth pathway for constructing organic heterostructures of interchangeable microblocks and adjustable optical output

Photon-Dipole-Spin Interactions in M(TCNE)x/P(VDF-TrFE) Multiferroic Heterostructure Available for Bimodal Control of Multistate Data-Storage.

Organic multiferroic heterostructure is one of the most promising structures for the future design of high-density flexible energy-efficient data storage. Here, organic ferromagnetic metal(tetracyanoethylene) (M(TCNE))x/ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) multiferroic heterostructures are fabricated, where the excited state in M(TCNE)x interacted with localized dipole in P(VDF-TrFE) provides a key link for the interfacial coupling. Thus, aligned dipoles in P(VDF-TrFE) by external electric field can affect the magnetization of Fe(TCNE)x effectively to result in a pronounced magnetization-voltage (M-V) hysteresis loop. Moreover, light-induced electron-hole pairs in Fe(TCNE)x with long lifetime effectively interact with the dipoles in P(VDF-TrFE) to lead to an effect in external light control of electric polarization of P(VDF-TrFE). Overall, the organic multiferroic heterostructure provides the possibility of realizing two storage modes, light control of dipole as well as electric field control of spin, which can broaden multifunctional applications of organic multiferroic materials in the area of multistate storage.

Gate-Tunable Positive and Negative Photoconductance in Near-Infrared Organic Heterostructures for In-Sensor Computing.

The rapid growth of sensor data in the artificial intelligence often causes significant reductions in processing speed and power efficiency. Addressing this challenge, in-sensor computing is introduced as an advanced sensor architecture that simultaneously senses, memorizes, and processes images at the sensor level. However, this is rarely reported for organic semiconductors that possess inherent flexibility and tunable bandgap. Herein, an organic heterostructure that exhibits a robust photoresponse to near-infrared (NIR) light is introduced, making it ideal for in-sensor computing applications. This heterostructure, consisting of partially overlapping p-type and n-type organic thin films, is compatible with conventional photolithography techniques, allowing for high integration density of up to 520 devices cm-2 with a 5µm channel length. Importantly, by modulating gate voltage, both positive and negative photoresponses to NIR light (1050nm) are attained, which establishes a linear correlation between responsivity and gate voltage and consequently enables real-time matrix multiplication within the sensor. As a result, this organic heterostructure facilitates efficient and precise NIR in-sensor computing, including image processing and nondestructive reading and classification, achieving a recognition accuracy of 97.06%. This work serves as a foundation for the development of reconfigurable and multifunctional NIR neuromorphic vision systems.

Constructed of Cd-based organic framework heterostructure material for solar-powered organic dye purification

A novel water-stable Cd-based organic framework material (Cd-MOF) has been synthesized based on the 4,4′-([2,2′-bipyridine]-6,6′-diylbis(oxy))phthalic acid (H4L) ligand and Cadmium nitrate tetrahydrate (Cd(NO3)2·4H2O) with a solvothermal method. We also prove that the rational design and preparation of Cd-MOF\\Ag heterojunctions by depositing Ag nanoparticles on the surface of Cd-MOF is an effective photocatalyst for the degradation of organic dyes in water. The photodegradation rates of RhB and MO were significantly improved under simulated sunlight conditions (AM1.5G), which reaching 0.68 and 1.549 min−1 g−1, respectively. The prominent performance is attributed to the efficient separation of photo-generated electrons and holes caused by the composite heterojunction of Cd-MOF/Ag. The surface plasmonic resonance (SPR) effect of Ag nanoparticles and the Schottky junction between Ag and Cd-MOF play crucial role in the photocatalytic degradation process. This work provides a new strategy for preparing photocatalysts and promoting the development of the degradation of organic dye pollutants in effluent with MOF-based material as photocatalysts.

UV to NIR Broadband Flexible Photodetector Based on Solution‐Processed MoS2/PDPP3T Inorganic–Organic Hybrid Heterostructures

AbstractMolybdenum disulfide (MoS2) is a 2D material with excellent electrical and optical properties, and developing a universal technology for the preparation of high‐performance MoS2‐based photodetector is extremely desirable. Here, a UV to NIR broadband flexible photodetector based on MoS2/(PDPP3T) inorganic–organic hybrid heterostructures is reported. In the experiment, high crystalline 2H‐phase few‐layer MoS2 nanoflakes are first prepared by optimized electrochemical intercalation of tetraheptylammonium cation (THA+) and ultrasound‐assisted exfoliation strategy. Thereafter, a narrow bandgap organic semiconductor PDPP3T is introduced to construct the MoS2/Poly(diketopyrrolopyrrolothiophrn) (PDPP3T) heterojunction. Experimental results reveal that the photodetector can have broadband photo response from 380 to 980 nm. Meanwhile, excellent responsivities and detectivity of 12.4 mA W−1, 2.2 × 1010 Jones at 380 nm and 0.1 mA W−1 and 5 × 108 Jones at 980 nm are achieved, which are ≈10 (UV band)/100 (NIR band) times high than that obtained on the pure MoS2‐based detector. Moreover, the flexibility of the device is investigated by conformal covering the device on a curved surface (R = 5 and 2.5 mm), it shows that the photo response remains almost the same as that measured on the planar substrate, indicating the possible application in the wearable electronics.

Heterostructure assembled by organic-molecule intercalated MoS2 and reduced graphene oxide for enhanced interface energy and supercapacitor performance

Organic molecule intercalation and heterostructure construction can optimize the capacitive storage of MoS2. To begin with, we choose MoO3 as the molybdenum source and polypyrrole (PPy) as the intercalation agent to synthesize the enlarged interlayer spacing MoS2 (MoS2-PPy). On this basis, MoS2-PPy@reduced graphene oxide (rGO) heterostructures are eventually fabricated. The electrochemical merits of rGO and MoS2-PPy can be combined through synergistic effects among the heterostructure. What's more, to examine the kinetics storage mechanisms of MoS2 samples, density functional theory (DFT) calculations have been done. It turns out the introduction of rGO enhanced the polarity of MoS2, which lead to stronger interface energy and additional capacitance. Additionally, for the involvement of rGO, the conductivity has been effectually elevated. Moreover, an AC//MoS2-PPy@rGO asymmetric flexible device is assembled, and it have an excellent energy density of 134.4 µWh cm−2 at a power density of 800 µW cm−2. This work paves the way for constructing organic-molecular intercalated-MoS2 based heterostructures in capacitive energy storage.

Printable Block Molecular Assemblies with Controlled Exciton Dynamics.

Creating hierarchical molecular block heterostructures, with the control over size, shape, optical, and electronic properties of each nanostructured building block can help develop functional applications, such as information storage, nanowire spectrometry, and photonic computing. However, achieving precise control over the position of molecular assemblies, and the dynamics of excitons in each block, remains a challenge. In the present work, the first fabrication of molecular heterostructures with the control of exciton dynamics in each block, is demonstrated. Additionally, these heterostructures are printable and can be precisely positioned using Direct Ink Writing-based (DIW) 3D printing technique, resulting in programable patterns. Singlet excitons with emission lifetimes on nanosecond or microsecond timescales and triplet excitons with emission lifetimes on millisecond timescales appear simultaneously in different building blocks, with an efficient energy transfer process in the heterojunction. These organic materials also exhibit stimuli-responsive emission by changing the power or wavelength of the excitation laser. Potential applications of these organic heterostructures in integrated photonics, where the versatility of fluorescence, phosphorescence, efficient energy transfer, printability, and stimulus sensitivity co-exist in a single nanowire, are foreseen.