Capillary-Confinement Crystallization for Monolayer Molecular Crystal Arrays

Supramolecular Electronics: Monolayer Assembly of Nonamphiphilic Molecules via Water Surface-Assisted Molecular Deposition

Utilizing softly confined self-assembly at the water surface represents a promising approach for the fabrication of two-dimensional molecular monolayers (2D MMs), which have predominantly been concentrated on amphiphilic organic compounds before. Herein, we introduce a straightforward method termed "water surface-assisted molecular deposition (WSAMD)" to organize nonamphiphilic molecules into dense monolayers with high reproducibility. To underscore the versatility and merit of this methodology in the field of supramolecular electronics, we have successfully fabricated a range of defect-free, uniform semiconducting polymer monolayers, featuring a thickness reflective of molecular architectures. The charge carrier mobility could reach 0.05 cm2 V-1 s-1 for holes and 3.5 × 10-4 cm2 V-1 s-1 for electrons, respectively, in p-type and n-type polymeric monolayers when tested as the active layer in field-effect transistors. Furthermore, in situ polymerization reactions can be exploited to generate conductive monolayers of macromolecules such as polybenzylaniline (PBnANI) and polypyrrole (PPy), where PBnANI monolayers exhibit channel length-dependent conductivity, up to 0.37 S cm-1. The advent of the WSAMD method heralds a significant leap forward in the advancement of molecular 2D materials, catalyzing new avenues of exploration within material chemistry.

Enhancing the Uniformity of Organic Field-Effect Transistors by a Single-Crystalline Layer-Controlled Active Channel

Despite remarkable improvement in the mobility of the organic field-effect transistors (OFETs) being achieved in past decades, the uniformity in electrical performance remains ambiguous, impeding their implantation in organic integrated circuits. The coefficient of variance (CV) in mobility of reported OFETs is typically larger than 8%, which is not adequate for building medium-to-large scale integrated circuits. In this work, it is shown that utilizing single-domain molecular monolayer crystals as the active channel can largely enhance the uniformity of OFETs. Benefiting from the sole molecular layer with long-range ordering, the OFETs exhibit uniformities in both channel transport and charge injection, thereby giving rise to a high average mobility of 11.64 cm2 V-1 s-1 and CV of only 2.57%. Statistical transmission length method evaluation is conducted, covering channel length from 3 to 21 µm, channel width from 90 to 170 µm, and a total OFET number of 370. The low contact resistance of 79.00 ± 7.00 Ω cm and high intrinsic mobility of 12.36 ± 0.45 cm2 V-1 s-1 are acquired with very high accuracy and reliability. As such, this work provides a practical way to enhance the uniformity of OFETs by a single-crystalline layer-controlled active channel toward their applications in integrated circuits.

Nanocrystal Array Engineering and Optoelectronic Applications of Organic Small-Molecule Semiconductors

Organic small-molecule semiconductor materials have attracted extensive attention because of their excellent properties. Due to the randomness of crystal orientation and growth location, however, the preparation of continuous and highly ordered organic small-molecule semiconductor nanocrystal arrays still face more challenges. Compared to organic macromolecules, organic small molecules exhibit better crystallinity, and therefore, they exhibit better semiconductor performance. The formation of organic small-molecule crystals relies heavily on weak interactions such as hydrogen bonds, van der Waals forces, and π-π interactions, which are very sensitive to external stimuli such as mechanical forces, high temperatures, and organic solvents. Therefore, nanocrystal array engineering is more flexible than that of the inorganic materials. In addition, nanocrystal array engineering is a key step towards practical application. To resolve this problem, many conventional nanocrystal array preparation methods have been developed, such as spin coating, etc. In this review, the typical and recent progress of nanocrystal array engineering are summarized. It is the typical and recent innovations that the array of nanocrystal array engineering can be patterned on the substrate through top-down, bottom-up, self-assembly, and crystallization methods, and it can also be patterned by constructing a series of microscopic structures. Finally, various multifunctional and emerging applications based on organic small-molecule semiconductor nanocrystal arrays are introduced.

Organic Semiconductor Single Crystal Arrays: Preparation and Applications

The study of organic semiconductor single crystal (OSSC) arrays has recently attracted considerable interest given their potential applications in flexible displays, smart wearable devices, biochemical sensors, etc. Patterning of OSSCs is the prerequisite for the realization of organic integrated circuits. Patterned OSSCs can not only decrease the crosstalk between adjacent organic field-effect transistors (OFETs), but also can be conveniently integrated with other device elements which facilitate circuits application. Tremendous efforts have been devoted in the controllable preparation of OSSC arrays, and great progress has been achieved. In this review, the general strategies for patterning OSSCs are summarized, along with the discussion of the advantages and limitations of different patterning methods. Given the identical thickness of monolayer molecular crystals (MMCs) which is beneficial to achieve super uniformity of OSSC arrays and devices, patterning of MMCs is also emphasized. Then, OFET performance is summarized with comparison of the mobility and coefficient of variation based on the OSSC arrays prepared by different methods. Furthermore, advances of OSSC array-based circuits and flexible devices of different functions are highlighted. Finally, the challenges that need to be tackled in the future are presented.

Dry Lithography Patterning of Monolayer Flexible Field Effect Transistors by 2D Mica Stamping

Organic field-effect transistors (OFETs) based on 2D monolayer organic semiconductors (OSC) have demonstrated promising potentials for various applications, such as light emitting diode (LED) display drivers, logic circuits, and wearable electrocardiography (ECG) sensors. To date, the fabrications of this class of highly crystallized 2D organic semiconductors (OSC) are dominated by solution shearing. As these organic active layers are only a few molecular layers thick, their compatibilities with conventional thermal evaporated top electrodes or sophisticated photolithography patterning are very limited, which also restricts their device density. Here, an electrode transfer stamp and a semiconductor patterning stamp are developed to fabricate OFETs with channel lengths down to 3 µm over a large area without using any chemicals or causing any damage to the active layer. 2D 2,9-didecyldinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (C₁₀ -DNTT) monolayer OFETs developed by this new approach shows decent performance properties with a low threshold voltage (V_TH ) less than 0.5 V, intrinsic mobility higher than 10 cm² V^-1 s^-1 and a subthreshold swing (SS) less than 100 mV dec^-1 . The proposed patterning approach is completely comparable with ultraflexible parylene substrate less than 2 µm thick. By further reducing the channel length down to 2 µm and using the monolayer OFET in an AC/DC rectifying circuit, the measured cutoff frequency is up to 17.3 MHz with an input voltage of 4 V. The newly proposed electrode transfer and patterning stamps have addressed the long-lasting compatibility problem of depositing electrodes onto 2D organic monolayer and the semiconductor patterning. It opens a new path to reduce the fabrication cost and simplify the manufacturing process of high-density OFETs for more advanced electronic or biomedical applications.

Low-Dimensional Organic Crystals: From Precise Synthesis to Advanced Applications

Low-dimensional organic crystals (LOCs) have attracted increasing attention recently for their potential applications in miniaturized optoelectronics and integrated photonics. Such applications are possible owing to their tunable physicochemical properties and excellent charge/photon transport features. As a result, the precise synthesis of LOCs has been examined in terms of morphology modulation, large-area pattern arrays, and complex architectures, and this has led to a series of appealing structure-dependent properties for future optoelectronic applications. This review summarizes the recent advances in the precise synthesis of LOCs in addition to discussing their structure-property relationships in the context of optoelectronic applications. It also presents the current challenges related to organic crystals with specific structures and desired performances, and the outlook regarding their use in next-generation integrated optoelectronic applications.

Recent Advances in Realizing Highly Aligned Organic Semiconductors by Solution-Processing Approaches

Solution-processing approaches are widely used for controlling the aggregation structure of organic semiconductors because they are fast, efficient, and have strong practicability. Effective regulation of the aggregation structure of molecules to achieve highly ordered molecular stacking is key to realizing effective carrier transport and high-performance devices. Numerous studies have achieved highly aligned organic semiconductors using different solution-processing approaches. This article provides a detailed review of the prevalent solution-processing technologies and emerging methods developed over the past few years for the alignment of organic semiconducting materials. These technologies and methods are classified according to the processing principle. This review focuses on the principles of different experimental techniques, improvements upon the conventional methods, and state-of-the-art performance of resulting devices. In addition, a brief discussion of the characteristics and development prospects of various methods is presented.

Photocatalytic hydrogen evolution based on carbon nitride and organic semiconductors

Photocatalytic hydrogen evolution (PHE) presents a promising way to solve the global energy crisis. Metal-free carbon nitride (CN) and organic semiconductors photocatalysts have drawn intense interests due to their fascinating properties such as tunable molecular structure, electronic states, strong visible-light absorption, low-cost etc. In this paper, the recent progresses of photocatalytic hydrogen production based on organic photocatalysts, including CN, linear polymers, conjugated porous polymers and small molecules, are reviewed, with emphasis on the various strategies to improve PHE efficiency. Finally, the possible future research trends in the organic photocatalysts are prospected.

Emerging Logic Devices beyond CMOS

Si-based complementary metal-oxide-semiconductor (CMOS) transistors for logic computing have represented the most essential foundation of digital electronic technologies for decades toward the modern information era. The continuous scaling down of the transistor feature size has promoted significant improvements in the computing performance while gradually tending to its limit. Ubiquitous intelligent technologies have quickly penetrated daily life, yielding a tremendous increase in highly data-centric computing applications. Hence, emerging logic devices extending and even transcending the existing CMOS technology are urgently needed to meet the rapidly growing demand for information processing capability, involving revolutionary innovations from material science and architecture design to device applications. This thus gives us the opportunity to realize logic devices for state-of-the-art computing that are fundamentally far beyond the current devices. In this Perspective, we discuss the recent innovative design strategies of emerging logic devices along with the opportunities and challenges, providing a promising avenue toward high-performance and diversiform logic computing in the post-Moore era.