Attributed to its advantages of super mechanical flexibility, very low-temperature processing, and compatibility with low cost and high throughput manufacturing, organic thin-film transistor (OTFT) ...technology is able to bring electrical, mechanical, and industrial benefits to a wide range of new applications by activating nonflat surfaces with flexible displays, sensors, and other electronic functions. Despite both strong application demand and these significant technological advances, there is still a gap to be filled for OTFT technology to be widely commercially adopted. This paper provides a comprehensive review of the current status of OTFT technologies ranging from material, device, process, and integration, to design and system applications, and clarifies the real challenges behind to be addressed.
A high‐performance ReS2‐based thin‐film transistor and photodetector with high on/off‐current ratio (104), high mobility (7.6 cm2 V−1 s−1), high photoresponsivity (2.5 × 107 A W−1), and fast temporal ...response (rising and decaying time of 670 ms and 5.6 s, respectively) through O2 plasma treatment is reported.
Studies on printable semiconductors and technologies have increased rapidly over recent decades, pioneering novel applications in many fields, such as energy, sensing, logic circuits, and information ...displays. The newest display technologies are already turning to metal oxide semiconductors, i.e., indium gallium zinc oxide, for the improvements needed to drive active matrix organic light‐emitting diodes. Convenience and portability will be realized with flexible and wearable displays in the future. This report summarizes recent progress on the development of solution‐processed thin film transistors, especially those deposited at low temperatures for next‐generation flexible smart displays. The first part provides an overview on the history and current status of displays. Then, recent advances in state‐of‐the‐art solution‐processed transistors based on different semiconductors are presented, including metal oxides, organic materials, perovskites, and carbon nanotubes. Finally, conclusions are drawn and the remaining challenges and future perspectives are discussed.
Semiconductor evolution has greatly promoted the development of high‐end displays over the past decades. Benefiting from the unique characteristics of low‐cost solution routes, recent progress in the development of solution‐processed thin film transistors (metal oxides, organics, carbon nanotubes, and perovskite) and their applications in next‐generation flexible smart displays are summarized. The challenges and prospectives for further development are also highlighted.
Printing technologies offer large‐area, high‐throughput production capabilities for electronics and sensors on mechanically flexible substrates that can conformally cover different surfaces. These ...capabilities enable a wide range of new applications such as low‐cost disposable electronics for health monitoring and wearables, extremely large format electronic displays, interactive wallpapers, and sensing arrays. Solution‐processed carbon nanotubes have been shown to be a promising candidate for such printing processes, offering stable devices with high performance. Here, recent progress made in printed carbon nanotube electronics is discussed in terms of materials, processing, devices, and applications. Research challenges and opportunities moving forward from processing and system‐level integration points of view are also discussed for enabling practical applications.
Printed electronics and sensors enable new applications ranging from low‐cost disposable analytical devices to large‐area sensor networks. Solution‐processed carbon nanotubes are an ideal material system for such applications as they offer stable devices with high performance.
Printed electronics enable the fabrication of large‐scale, low‐cost electronic devices and systems, and thus offer significant possibilities in terms of developing new electronics/optics applications ...in various fields. Almost all electronic applications require information processing using logic circuits. Hence, realizing the high‐speed operation of logic circuits is also important for printed devices. This report summarizes recent progress in the development of printed thin‐film transistors (TFTs) and integrated circuits in terms of materials, printing technologies, and applications. The first part of this report gives an overview of the development of functional inks such as semiconductors, electrodes, and dielectrics. The second part discusses high‐resolution printing technologies and strategies to enable high‐resolution patterning. The main focus of this report is on obtaining printed electrodes with high‐resolution patterning and the electrical performance of printed TFTs using such printed electrodes. In the final part, some applications of printed electronics are introduced to exemplify their potential.
High‐resolution printing technologies enable high‐resolution patterning and fast operation of printed electronics. Recent progress in printed thin‐film transistors and integrated circuits is summarized, in terms of their materials, printing technologies, and applications. The development of functional inks, high‐resolution printing technologies, and applications of printed electronics are summarized and discussed to exemplify the potential of printed electronics.
At the convergence of organic electronics and biology, organic bioelectronics attracts great scientific interest. The potential applications of organic semiconductors to reversibly transmit ...biological signals or stimulate biological tissues inspires many research groups to explore the use of organic electronics in biological systems. Considering the surfaces of movable living tissues being arbitrarily curved at physiological environments, the flexibility of organic bioelectronic devices is of paramount importance in enabling stable and reliable performances by improving the contact and interaction of the devices with biological systems. Significant advances in flexible organic bioelectronics have been achieved in the areas of flexible organic thin film transistors (OTFTs), polymer electrodes, smart textiles, organic electrochemical ion pumps (OEIPs), ion bipolar junction transistors (IBJTs) and chemiresistors. This review will firstly discuss the materials used in flexible organic bioelectronics, which is followed by an overview on various types of flexible organic bioelectronic devices. The versatility of flexible organic bioelectronics promises a bright future for this emerging area.
Organic bioelectronics attracts much attention due to the unique electronic properties, biocompatibility, mechanical flexibility, easy fabrication, and low cost. Flexible devices are potentially useful in many biological applications because the surfaces of living tissues are always arbitrarily curved. This review focuses mainly on the operation and application of flexible bioelectronic devices reported in recent years.
Thanks to its strong X‐ray absorption and large carrier diffusion length, perovskites have demonstrated excellent performance for X‐ray detection. Combination of perovskite with thin‐film transistor ...(TFT) arrays to construct flat‐panel X‐ray imager (FPXI) is required for X‐ray imaging, yet this is rarely reported. Solution processing of perovskite thick film onto TFT can enable the electronic connection, however the amounts of pinholes inevitably form during the solvent evaporation and result in a porous film with deteriorated performance and stability. Here a novel strategy is raised to achieve high‐quality perovskite thick films for TFT integration via soft‐pressing and in situ polymerization of multi‐functional binder (TMTA). The combined process largely eliminates the pinholes, improves the surface smoothness, passivates grains boundaries, reduces ionic migration, and improves stability. Accordingly, a compact and smooth MAPbI3 thick film integrating with TFT arrays is prepared for flat‐panel X‐ray imaging. The largest film (28 × 28 cm2) is obtained with the state‐of‐the‐art performance (ratio of sensitivity to noise current: 1.41 × 1011 µC Gy−1 A−1) among polycrystalline films. It is hoped that the work provides guidance for fabricating compact perovskite thick films and push perovskite FPXI one step further for low‐dose X‐ray imaging.
By combining soft‐pressing and a multi‐functional polymerizable binder (TMTA), MAPbI3 thick film (≈400 µm) with compact structure, smooth surface, passivated grain boundaries, large area, high uniformity, and state‐of‐the‐art detection performance is achieved. The high‐quality perovskite thick film is successfully integrated with back‐end thin‐film transistor arrays and excellent large‐area X‐ray imaging is read out.
Eco‐friendly and low‐cost cellulose nanofiber paper (nanopaper) is a promising candidate as a novel substrate for flexible electron device applications. Here, a thin transparent nanopaper‐based ...high‐mobility organic thin‐film transistor (OTFT) array is demonstrated for the first time. Nanopaper made from only native wood cellulose nanofibers has excellent thermal stability (>180 °C) and chemical durability, and a low coefficient of thermal expansion (CTE: 5–10 ppm K‐1). These features make it possible to build an OTFT array on nanopaper using a similar process to that for an array on conventional glass. A short‐channel bottom‐contact OTFT is successfully fabricated on the nanopaper by a lithographic and solution‐based process. Owing to the smoothness of the cast‐coated nanopaper surface, a solution processed organic semiconductor film on the nanopaper comprises large crystalline domains with a size of approximately 50–100 μm, and the corresponding TFT exhibits a high hole mobility of up to 1 cm2V‐1 s‐1 and a small hysteresis of below 0.1 V under ambient conditions. The nanopaper‐based OTFT also had excellent flexibility and can be formed into an arbitrary shape. These combined technologies of low‐cost and eco‐friendly paper substrates and solution‐based organic TFTs are promising for use in future flexible electronics application such as flexible displays and sensors.
Optically transparent paper is an attractive candidate for the substrate of eco‐friendly and low‐cost flexible electron devices. Here, a high‐mobility organic thin‐film transistor (TFT) array is demonstrated on a 20‐μm‐thick transparent cellulose nanofibers paper. The fabricated short channel TFTs exhibit a high mobility of up to 1 cm2V‐1s‐1 and air stability. The nanopaper‐based structure also has mechanical flexibility.
Aggregation‐structure formation of conjugated polymers is a fundamental problem in the field of organic electronics and remains poorly understood. Herein, the molar mass dependence of the aggregation ...structure of a high‐mobility conjugated copolymer (TDPP‐Se) comprising thiophene‐flanked diketopyrrolopyrrole and selenophene is thoroughly shown. Five batches of TDPP‐Se are prepared with the number‐average molecular weights (Mn) varied greatly from 21 to 135 kg mol−1. Small‐angle neutron scattering and transmission electron microscopy are combined to probe the solution structure of these polymers, consistently using a deuterated solvent. All the polymers adopt 1D rod‐like aggregation structures and the radius of the 1D rods is not sensitive to the Mn, while the length increases monotonically with Mn. By utilizing the ordered packing of the aggregated structure in solution, a highly aligned and ordered film is prepared and, thereafter, a reliable hole mobility of 13.8 cm2 V−1 s−1 is realized in organic thin‐film transistors with the moderate Mn batch via bar coating. The hole mobility is among the highest values reported for diketopyrrolopyrrole‐based polymers. This work paves the way to visualize the real aggregated structure of polymer semiconductors in solution and sheds light on the microstructure control of high‐performance electronic devices.
The molar mass dependence on aggregation structure evolution and charge transport of TDPP‐Se is thoroughly examined by neutron scattering and complementary techniques. The rod‐like preaggregate with moderate length favors a highly aligned and ordered structure by bar coating. Hence, a reliable hole mobility up to ≈14 cm2 V−1 s−1 is recorded for thin‐film transistors using diketopyrrolopyrrole‐based polymers.
Plasma‐enhanced atomic layer deposition (PEALD)‐based bilayer IZO (back channel)/IGZO top‐gate thin‐film transistors (TFTs) with different IZO and IGZO layer thicknesses are fabricated to evaluate ...the correlation between thickness and electrical characteristics/reliability caused by dual‐channel modulation. The dual‐channel formed by IZO stacked on the backchannel improves both mobility and reliability of devices as the IZO layer thickness increases. In the TCAD simulation, as the thickness of IZO increases, the current flowing through the IZO channel among the dual channels increases and the main channel transition from IGZO to IZO occurs above a certain IZO layer thickness. The main channel transition to IZO, which has high mobility and is located in the backchannel away from the gate insulator (GI), leads to a mobility increase with a lower threshold voltage (Vth) shift and a remarkable improvement of reliability deteriorated by the GI. As a result, PEALD‐based IZO/IGZO TG TFTs exhibit both high mobility (≈40 cm2 V−1 s−1) and high stability (ΔVth = ‐0.07 V) of a positive bias temperature stress up to 10 800 s. This suggests that ALD‐based dual‐channel regulation by nanoscale thickness control of the stacking oxide semiconductor can overcome the trade‐off between mobility and reliability.
A plasma‐enhanced atomic layer deposition (PEALD)‐based InZnO/InGaZnO top‐gate thin‐film transistor (TFT) is fabricated to satisfy both high mobility and stability. As dual‐channel modulation through nanoscale thickness control, the InZnO/InGaZnO TFT exhibits a mobility of ≈40 cm2 V−1 s−1 and stability of ∆Vth = –0.07 V (@ 2 MV cm−1, 60 °C, 10 800 s). It is expected that dual‐channel modulation can overcome the limitations of the mobility and stability trade‐offs.
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