Two-dimensional (2D) crystals of organic semiconductors (2DCOS) have attracted attention for large-area and low-cost flexible optoelectronics. However, growing large 2DCOS in controllable ways and transferring them onto technologically important substrates, remain key challenges. Herein we report a facile, general, and effective method to grow 2DCOS up to centimeter size which can be transferred to any substrate efficiently. The method named “solution epitaxy” involves two steps. The first is to self-assemble micrometer-sized 2DCOS on water surface. The second is epitaxial growth of them into millimeter or centimeter sized 2DCOS with thickness of several molecular layers. The general applicability of this method for the growth of 2DCOS is demonstrated by nine organic semiconductors with different molecular structures. Organic field-effect transistors (OFETs) based on the 2DCOS demonstrated high performance, confirming the high quality of the 2DCOS.

Two-dimensional (2D) crystals of organic semiconductors (2DCOS) have attracted attention for large-area and low-cost flexible optoelectronics. However, growing large 2DCOS in controllable ways and transferring them onto technologically important substrates, remain key challenges. Herein we report a facile, general, and effective method to grow 2DCOS up to centimeter size which can be transferred to any substrate efficiently. The method named “solution epitaxy” involves two steps. The first is to self-assemble micrometer-sized 2DCOS on water surface. The second is epitaxial growth of them into millimeter or centimeter sized 2DCOS with thickness of several molecular layers. The general applicability of this method for the growth of 2DCOS is demonstrated by nine organic semiconductors with different molecular structures. Organic field-effect transistors (OFETs) based on the 2DCOS demonstrated high performance, confirming the high quality of the 2DCOS.

One-dimensional (1D) solid-state supramolecular structures based on porphyrin chromophores arouse numerous expectations from the interdisciplinary scientific communities of supramolecular chemistry and advanced soft materials science. This stems from the intrinsic assembly capability of porphyrins to form various well-defined 1D assemblies, which have broad opportunities in the fields of advanced soft matter. A brief review on 1D porphyrin micro-/nanoassemblies constructed via surfactant-assisted self-assembly is presented here, in terms of addressing new ideas recently developed for controlled assembly, hierarchical organization, and new-type functional surfactants etc. The functionalization of the as-assembled 1D structures with regard to supramolecular photocatalysis, non-linear optics, nanoelectronic gas sensors, photoelectrochemical solar cells, etc. is highlighted.

A new crystal of a charge-transfer (CT) complex was prepared through supramolecular assembly and it has unique two-dimensional (2D) morphology. The CT nature of the ground and excited states of this new Bpe-TCNB cocrystal (BTC) were confirmed by electron spin resonance measurements, spectroscopic studies, and theoretical calculations, thus providing a comprehensive understanding of the CT interactions in organic donor–acceptor systems. And the lowest CT₁ excitons are responsible for the efficient photoluminescence (Φ_PL=19 %), which can actively propagate in individual 2D BTCs without anisotropy, thus implying that the optical waveguide property of the crystal is not related to the molecular stacking structure. This unique 2D CT cocrystal exhibits potential for use in functional photonic devices in the next-generation optoelectronic communications.

A new crystal of a charge-transfer (CT) complex was prepared through supramolecular assembly and it has unique two-dimensional (2D) morphology. The CT nature of the ground and excited states of this new Bpe-TCNB cocrystal (BTC) were confirmed by electron spin resonance measurements, spectroscopic studies, and theoretical calculations, thus providing a comprehensive understanding of the CT interactions in organic donor–acceptor systems. And the lowest CT₁ excitons are responsible for the efficient photoluminescence (Φ_PL=19 %), which can actively propagate in individual 2D BTCs without anisotropy, thus implying that the optical waveguide property of the crystal is not related to the molecular stacking structure. This unique 2D CT cocrystal exhibits potential for use in functional photonic devices in the next-generation optoelectronic communications.

Obvious differentiated response of organic phototransistors (OPTs) to the lights with different wavelengths is a challenge but a prerequisite for wavelength-selective applications. In this manuscript, highly UV-sensitive OPTs are fabricated based on benzo[1,2-b:4,5-b′]dithiophene dimers (BBDT, BBDTE, and BBDTY). The BBDTE-based organic single-crystal transistors (OSCTs), which show carrier mobility up to 1.62 cm² V⁻¹ s⁻¹, exhibit a maximum photoresponsivity up to 9821 A W⁻¹ and a maximum photosensitivity up to 10⁵ towards UV light (37 μW cm⁻²), and the photosensitivity observed within tested light intensity range is unexpectedly stable. The BBDTY-based OPTs also exhibit differentiated response between UV and visible lights, even with thin-film state of organic semiconductor, and the highest photoresponsivity and photosensitivity to UV light reached 9336 A W⁻¹ and 4429, respectively. This selective and highly sensitive performance enables unsaturated bond-linked benzo[1,2-b:4,5-b′]dithiophene dimers promising candidates for UV detectors.

Graphene-based ultrathin films with tunable performances, controlled thickness, and high stability are crucial for their uses. The currently existing protocols, however, could hardly simultaneously meet these requirements. Using amino-substituted π-conjugated compounds, including 1,4-diaminobenzene (DABNH2), benzidine (BZDNH2), and 5,10,15,20-tetrakis (4-aminophenyl)-21H,23H-porphine (TPPNH2), as cross-linkages, a new protocol through which graphene oxide (GO) nanosheets can be anchored on solid supports with a high stability and controlled thickness via a layer-by-layer method is presented. A thermal annealing leads to the reduction of the films, and the qualities of the samples can be inherited by the as-produced reduced GO films (RGO). When RGO films are integrated as source/drain electrodes in OFETs, tunable performances can be realized. The devices based on the BZDNH2-crosslinked RGO electrodes exhibit similar electrical behaviors as those based on the non-π-conjugated compound crosslinked electrodes, while improved performances can be gained when those crosslinked by DABNH2 are used. The performances can be further improved when RGO films crosslinked by TPPNH2 are employed. This work likely paves a new avenue for graphene-based films of tunable performances, controlled thickness, and high stability.

“Regioselectivity deposition” method is developed to pattern silver electrodes facilely and efficiently by solution-process with high resolution (down to 2 μm) on different substrates in A4 paper size. With the help of this method, large-area, flexible, high-performance polymer field-effect transistors based on the silver electrodes and polyimide insulator are fabricated with bottom-contact configuration by all-solution processes. The polymer devices exhibit high performance with average field-effect mobility over 1.0 cm² V⁻¹ s⁻¹ (the highest mobility up to 1.5 cm² V⁻¹ s⁻¹) and excellent environmental stability and flexibility, indicating the cost effectiveness of this method for practical applications in organic electronics.

Solution processibility is one of the most intriguing properties of organic semiconductors. However, it is difficult to find a suitable solvent and solution process for most semiconductors. For example, metal phthalocyanines (MPcs) are only soluble in non-volatile solvents, which prevent their applications from solution process. For the first time, vectorial diffusion is utilized for solution processing of MPcs. The obtained large F₁₆CuPc and α-phase CuPc crystals and the efficient phase separation of them suggest the vectorial diffusion process is as slow as a self-assembly process, which is helpful to yield large crystals and purify the semiconductors. This method, which only uses common commercial solvents without any complex and expensive instruments and high-temperature operation, provides a facile approach for purification of organic semiconductors and growth of their crystals in large quantities.

Remarkable progress has been made in developing high performance organic field-effect transistors (OFETs) and the mobility of OFETs has been approaching the values of polycrystalline silicon, meeting the requirements of various electronic applications from electronic papers to integrated circuits. In this review, the key points for development of high mobility OFETs are highlighted from aspects of molecular engineering, process engineering and interface engineering. The importance of other factors, such as impurities and testing conditions is also addressed. Finally, the current challenges in this field for practical applications of OFETs are further discussed.

Highly stable graphene oxide (GO)-based multilayered ultrathin films can be covalently immobilized on solid supports through a covalent-based method. It is demonstrated that when (3-aminopropyl) trimethoxysilane (APTMS), which works as a covalent cross-linking agent, and GO nanosheets are assembled in an layer-by-layer (LBL) manner, GO nanosheets can be covalently grafted on the solid substrate successfully to produce uniform multilayered (APTMS/GO)N films over large-area surfaces. Compared with conventional noncovalent LBL films constructed by electrostatic interactions, those assembled using this covalent-based method display much higher stability and reproducibility. Upon thermal annealing-induced reduction of the covalent (APTMS/GO)N films, the obtained reduced GO (RGO) films, (APTMS/RGO)N, preserve their basic structural characteristics. It is also shown that the as-prepared covalent (APTMS/RGO)N multilayer films can be used as highly stable source/drain electrodes in organic field-effect transistors (OFETs). When the number of bilayers of the (APTMS/RGO)N film exceeds 2 (ca. 2.7 nm), the OFETs based on (APTMS/RGO)N electrodes display much better electrical performance than devices based on 40 nm Au electrodes. The covalent protocol proposed may open up new opportunities for the construction of graphene-based ultrathin films with excellent stability and reproducibility, which are desired for practical applications that require withstanding of multistep post-production processes.

Nanogap electrodes (namely, a pair of electrodes with a nanometer gap) are fundamental building blocks for the fabrication of nanometer-sized devices and circuits. They are also important tools for the examination of material properties at the nanometer scale, even at the molecular scale. In this review, the techniques for the fabrication of nanogap electrodes, the preparation of assembled devices based on the nanogap electrodes, and the potential application of these nanodevices for analysis of material properties are introduced. The history, the research status, and the prospects of nanogap electrodes are also discussed.

High-performance and battery drivable organic single-crystalline transistors with operational voltages ≤ 2.0 V are demonstrated using high-quality copper phthalocyanine (CuPc) single-crystalline nanoribbons and ultrathin polymer nanodielectrics. The ultrathin polymer nanodielectric is synthesized by grafting a ca. 10 nm poly(methyl methacrylate) (PMMA) brush on a silicon surface via surface-initiated atom-transfer radical polymerization (SI-ATRP). This surface-grafted nanodielectric exhibits a large capacitance, excellent insulating property, and good compatibility with organic semiconductors. The realization of a low operational voltage for battery driving at high performance, together with the merits of surface grafting of a nanodielectric, as well as the mechanical flexibility of the organic nanoribbon, suggests a bright future for use of these transistors in low-cost and flexible circuits.

This paper describes a simple, vapor-phase route for the synthesis of metastable α-phase copper-phthalocyanine (CuPc) single-crystal nanowires through control of the growth temperature. The influence of the growth temperature on the crystal structures, morphology, and size of the CuPc nanostructures is explored using X-ray diffraction (XRD), optical absorption, and transmission electron microscopy (TEM). α-CuPc nanowires are successfully incorporated as active semiconductors in field-effect transistors (FETs). Single nanowire devices exhibit carrier mobilities and current on/off ratios as high as 0.4 cm² V⁻¹ s⁻¹ and >10⁴, respectively.

Charge transport in organic semiconductors is strongly dependent on their molecular packing modes in the solid state. Therefore, understanding the relationship between molecular packing and charge transport is imperative, both experimentally and theoretically. However, so far, the fundamental effects of solid-state packing and molecular interactions (e.g. NH⋅⋅⋅π) on charge transport need further elucidation. Herein, indolo[3,2-b]carbazole (ICZ) and a derivative thereof are used as examples to approach this scientific target. An interesting insight obtained thereby is that NH⋅⋅⋅π interactions among ICZ molecules facilitate charge transport for higher mobility. Subtle changes in the of NH⋅⋅⋅π interactions can significantly influence both the molecular packing and the charge-transport properties. Therefore, a method for exploiting intermolecular NH⋅⋅⋅π interactions would yield novel molecular systems with designable characteristics.