A Dewetting-Induced Assembly Strategy for Precisely Patterning Organic Single Crystals in OFETs

Capillary-Assisted Confinement Assembly for Advanced Sensor Fabrication: From Superwetting Interfaces to Capillary Bridge Patterning

Precise patterning of sensing materials, particularly the long-range-ordered assembly of micro/nanostructures, is pivotal for improving sensor performance, facilitating miniaturization, and enabling seamless integration. This paper examines the importance of interfacial confined assembly in sensor patterning, including gas-liquid and liquid-liquid confined assembly, wettability-assisted or microstructure-assisted solid-liquid interfacial confined assembly, and tip-induced confined assembly. The application of capillary bridge confined assembly technology in chemical sensors, flexible electronics, and optoelectronics is highlighted. The advantages of capillary bridge confined assembly technology include the ability to achieve high-resolution patterning, scalability, and material arrangement in long-range order. It is, therefore, an ideal processing platform for next-generation sensors. Finally, the broad prospects of this technology in the miniaturization and integration of high-performance multifunctional sensors are discussed.

Conjugated Polymer-Based Photo-Crosslinker for Efficient Photo-Patterning of Polymer Semiconductors

Photo-patterning of polymer semiconductors using photo-crosslinkers has shown potential for organic circuit fabrication via solution processing techniques. However, the performance of patterning, including resolution (R), UV light exposure dose, sensitivity (S), and contrast (γ), remains unsatisfactory. In this study, a novel conjugated polymer based photo-crosslinker (PN3, Figure 1a) is reported for the first time, which entails phenyl-substituted azide groups in its side chains. Due to the potential π-π interactions between the conjugated backbone of PN3 and those of polymer semiconductors, PN3 exhibits superior miscibility with polymer semiconductors compared to the commonly used small molecule photo-crosslinker 4Bx (Figure 1a). Consequently, photo-patterning of polymer semiconductors with PN3 demonstrates improved performance with much lower UV light exposure dose, higher S and higher γ compared to 4Bx. By utilizing electron beam lithography, patterned arrays of polymer semiconductors with resolutions down to 500 nm and clearer edges are successfully fabricated using PN3. Furthermore, patterned arrays of PDPP4T, the p-type semiconductor (Figure 1b), after being doped, can function as source-drain electrodes for fabricating field-effect transistors (FETs) with comparable charge mobility and significantly lower sub-threshold swing value compared to those with gold electrodes.

Flexible Electronics Based on Organic Semiconductors: from Patterned Assembly to Integrated Applications

Organic flexible electronic devices are at the forefront of the electronics as they possess the potential to bring about a major lifestyle revolution owing to outstanding properties of organic semiconductors, including solution processability, lightweight and flexibility. For the integration of organic flexible electronics, the precise patterning and ordered assembly of organic semiconductors have attracted wide attention and gained rapid developments, which not only reduces the charge crosstalk between adjacent devices, but also enhances device uniformity and reproducibility. This review focuses on recent advances in the design, patterned assembly of organic semiconductors, and flexible electronic devices, especially for flexible organic field-effect transistors (FOFETs) and their multifunctional applications. First, typical organic semiconductor materials and material design methods are introduced. Based on these organic materials with not only superior mechanical properties but also high carrier mobility, patterned assembly strategies on flexible substrates, including one-step and two-step approaches are discussed. Advanced applications of flexible electronic devices based on organic semiconductor patterns are then highlighted. Finally, future challenges and possible directions in the field to motivate the development of the next generation of flexible electronics are proposed.

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.

An Efficient Diazirine-Based Four-Armed Cross-linker for Photo-patterning of Polymeric Semiconductors

A diazirine-based four-armed cross-linker (4CNN) with a tetrahedron geometry is presented for efficient patterning of polymeric semiconductors by photo-induced carbene insertion. After blending of 4CNN with no more than 3 % (w/w), photo-patterning of p-, n-, and ambipolar semiconducting polymers with side alkyl chains was achieved; regular patterns with size as small as 5 μm were prepared with appropriate photomasks after 365 nm irradiation for just 40 s. The interchain packing order and the thin film morphology were nearly unaltered after the cross-linking and the semiconducting properties of the patterned thin films were mostly retained. A complementary-like inverter with a gain value of 112 was constructed easily by two steps of photo-patterning of the p-type and n-type semiconducting polymers. The results show that 4CNN is a new generation of cross-linker for the photo-patterning of polymeric semiconductors for all-solution-processible flexible electronic devices.

Large scale assembly of nanomaterials: mechanisms and applications

The large scale assembly of nanomaterials is the crucial factor contributing to the creation of high-performance devices based on nanotechnology, which have flourished in an unprecedented manner. In this review, we summarize the main methods for the large-scale integration of nanomaterials, including the bubble blown assembly, capillary-force-assisted assembly, electric-field-assisted assembly, and Langmuir-Blodgett assembly. Assembly principles and general procedures of these methods are described in detail. Then, instances of nanomaterials assembled at a large scale with different dimensional orders are introduced. The alignment and precise location of nanomaterials in a large area are emphasized here, which is the prerequisite for further applications. Additionally, we also focused on the recently advanced, efficient, and versatile devices that are mainly assembled using the aforementioned methods, including sensors, photovoltaic devices, field-effect transistors, and photodetectors. Finally, prospective and potential opportunities are presented.

Asymmetric Wettability Interfaces Induced a Large-Area Quantum Dot Microstructure toward High-Resolution Quantum Dot Light-Emitting Diodes

Precisely patterning large-area quantum dot (QD) nanoparticles is an essential technique for enhancing high-resolution and high-performance in the next-generation display-QLEDs. However, conventional solution-based assembly techniques suffer from trade-offs between large-scale and spatial precision. As such, large nondefect areas and ordered stacking of QD assembly architectures are difficult to achieve, and both are essential to fabricating a high-performance device. Herein, we demonstrate a facile method for assembling the QD nanoparticles into a microstructure using an asymmetric wettability template to regulate the dewetting process. The wettability difference of the interface induces the continuous liquid film to recede into individual liquid bridges, which enabled unidirectional dewetting and regulated the QD solution mass transport. In addition, because of the asymmetric wettability between the substrate and template, large-scale, ultrafine (1 μm), and highly flat microwire QD arrays with the precise position and strict alignment are easily assembled and transferred onto the target substrate. The method has been further introduced into the fabrication of high-resolution patterned QLED devices, with maximum electroluminescence values of 73 490, 4357, and 950 cd/m² for green, red, and blue, respectively. This research provides a novel and facile perspective for manufacturing high-resolution and high-performance patterned QLED devices.

Fabrication of Two-Dimensional Crystalline Organic Films by Tilted Spin Coating for High-Performance Organic Field-Effect Transistors

We developed a facile method for fabricating large-area, two-dimensional (2D), organic, highly crystalline films and extended it to organic thin-film transistor arrays. Tilted spinning provided oriented flow at the three-phase contact line, and a 2D crystalline film that consisted of layer-by-layer stacked 2,7-diocty[1]benzothieno[3,2- b]benzothiophene (C₈-BTBT) was obtained facilely for organic thin-film transistors (OTFTs). The extracted field-effect mobility is 4.6 cm² V^-1 s^-1, but with nonideal features. By applying this method to microdroplet arrays, an oriented crystal was fabricated, and the channel region for OTFTs was covered by adjusting the spinning speed. By tuning the tilt angle (θ) of the revolving substrate, we fabricated high-performance OTFT arrays with average and maximum mobilities of 7.5 and 10.1 cm² V^-1 s^-1, respectively, which exhibited high reliability factors of over 90% and were close to that of ideal transistors. These results suggest that high-quality crystalline films can be obtained via a facile tilted-spinning method.