Organic Field-effect Transistor Arrays Research Articles

Breaking Fundamental Limitation of Flow-Induced Anisotropic Growth for Large-Scale and Fast Printing of Organic Single-Crystal Films.

Advanced organic electronic technologies have put forward a pressing demand for cost-effective and high-throughput fabrication of organic single-crystal films (OSCFs). However, solution-printed OSCFs are typically plagued by the existence of abundant structural defects, which pose a formidable challenge to achieving large-scale and high-performance organic electronics. Here, it is elucidated that these structural defects are mainly originated from printing flow-induced anisotropic growth, an important factor that is overlooked for too long. In light of this, a surfactant-additive printing method is proposed to effectively overcome the anisotropic growth, enabling the deposition of uniform OSCFs over the wafer scale at a high speed of 1.2 mm s-1 at room temperature. The resulting OSCF exhibits appealing performance with a high average mobility up to 10.7 cm2 V-1 s-1, which is one of the highest values for flexible organic field-effect transistor arrays. Moreover, large-scale OSCF-based flexible logic circuits, which can be bent without degradation to a radius as small as 4.0 mm and over 1000 cycles are realized. The work provides profound insights into breaking the limitation of flow-induced anisotropic growth and opens new avenues for printing large-scale organic single-crystal electronics.

Precise patterning of single crystal arrays of organic semiconductors by a patterned microchannel dip-coating method for organic field-effect transistors

A patterned microchannel dip-coating method was developed for achieving high-quality organic single crystal arrays, ensuring the fabrication of discrete organic field-effect transistor arrays with a high average mobility of 1.5 cm2V−1s−1.

Solution-Processed Centimeter-Scale Highly Aligned Organic Crystalline Arrays for High-Performance Organic Field-Effect Transistors.

Solution-printed organic single-crystalline films hold great potential for achieving low-cost manufacturing of large-area and flexible electronics. For practical applications, organic field-effect transistor arrays must exhibit high performance and small device-to-device variation. However, scalable fabrication of highly aligned organic crystalline arrays is rather difficult due to the lack of control over the crystallographic orientation, crystal uniformity, and thickness. Here, a facile solution-printing method to fabricate centimeter-sized highly aligned organic crystalline arrays with a thickness of a few molecular layers is reported. In this study, the solution shearing technique is used to produce large-area, organic highly crystalline thin films. Water-soluble ink is printed on the hydrophobic surface of organic crystalline films, to selectively protect it, followed by etching. It is shown that the addition of a surfactant dramatically changes the fluid drying dynamics and increases the contact line friction of the aqueous solution to the underlying nonwetting organic crystalline film. As a result, centimeter-scale highly aligned organic crystalline arrays are successfully prepared on different substrates. The devices based on organic crystalline arrays show good performance and uniformity. This study demonstrates that solution printing is close to industrial application and also expands its applicability to various printed flexible electronics.

Flexible organic field-effect transistor arrays for wearable neuromorphic device applications.

With the advent of wearable microelectronic devices in the interdisciplinary bio-electronics research field, synaptic devices with capability of neuromorphic computing are attracting more and more attention as the building blocks for the next generation computing structure. Conventional flash-like synaptic transistors are built on rigid solid-state substrates, and the inorganic materials and the high-temperature processing steps have severely limited their applications in various flexible electronic devices and systems. Here, flexible organic flash-like synaptic devices have been fabricated on a flexible substrate with the organic C8-BTBT as the conducting channel. The device exhibits a memory window greater than 20 V and excellent synaptic functions including short/long-term synaptic plasticity and spike-timing-dependent plasticity. In addition, even under the bending condition (7 mm bending radius), the transistor can still stably achieve a variety of synaptic functions. This work shows that low-temperature processing technology with the integration of organic materials can pave a promising pathway for the realization of flexible synaptic systems and the future development of wearable electronic devices.

Highly stable and flexible transparent conductive polymer electrode patterns for large-scale organic transistors

The application of conductive polymer polypyrrole (PPY) towards transparent and flexible electronics has been demonstrated by a photolithography-compatible technique. The oxygen plasma pretreatment was found to be important for successful fabrication of PPY electrode patterns on flexible poly(ethylene terephthalate) (PET). By the patterning process of PPY, the transparency of PPY electrode can be improved up to >80% over the visible spectrum, which combined with the excellent chemical and physical stability of PPY shows the huge potential of PPY electrode as flexible transparent conductive electrode. In addition, PPY provides better interface connection for uniform deposition of organic semiconductor thin film. These outstanding advantages in PPY, coupled with selection of a novel anti-solvent and water-tolerant elastic dielectric, enable the photolithographic PPY patterns to be used for fabrication of large-scale flexible transparent organic field-effect transistor arrays. These results open up the capability of PPY as flexible transparent electrode for flexible organic devices, and exhibit a strong potential of PPY electrode patterns for future large-scale high-precision flexible electronics.

Array of Organic Field-Effect Transistor for Advanced Sensing

Organic electronics, taking advantage of flexibility and environmental sensitivity, have been investigated for diverse applications including flexible displays, wearable electronic devices and solar cells. A compelling additional application of organic electronics is sensing, especially of chemicals, pressure and light. As the key materials of organic electronics, organic semiconductors have been intensively studied, and have achieved mobility and stability good enough to be applied in various electronic circuits and systems with moderate complexity. This article presents a brief review of the transistor array systems, focusing on using arrays of organic field-effect transistors (OFETs) for advanced sensing applications. OFET-based sensors are able to transduce an environment changing event into an electric signal by utilizing the unique combination of electric and environmental sensitive properties of organic semiconductors. Additionally, designing the microstructure and introducing the interfacial interaction inside the OFETs are another approaches to provide increased sensing capability to the devices. By incorporating the OFET sensors into arrays, advanced sensing can be further realized, such as tactile sensing, pattern imaging, skin-like temperature detecting and electronic nose. It is expected that by reviewing these OFET sensor arrays, this article could provide an inspiration for advanced applications based on organic electronic circuits and systems.

Organic field-effect transistor-based gas sensors.

Organic field-effect transistors (OFETs) are one of the key components of modern organic electronics. While the past several decades have witnessed huge successes in high-performance OFETs, their sophisticated functionalization with regard to the responses towards external stimulations has also aroused increasing attention and become an important field of general concern. This is promoted by the inherent merits of organic semiconductors, including considerable variety in molecular design, low cost, light weight, mechanical flexibility, and solution processability, as well as by the intrinsic advantages of OFETs including multiparameter accessibility and ease of large-scale manufacturing, which provide OFETs with great potential as portable yet reliable sensors offering high sensitivity, selectivity, and expeditious responses. With special emphases on the works achieved since 2009, this tutorial review focuses on OFET-based gas sensors. The working principles of this type of gas sensors are discussed in detail, the state-of-the-art protocols developed for high-performance gas sensing are highlighted, and the advanced gas discrimination systems in terms of sensory arrays of OFETs are also introduced. This tutorial review intends to provide readers with a deep understanding for the future design of high-quality OFET gas sensors for potential uses.

Flexible air-stable three-dimensional polymer field-effect transistors with high output current density

Flexible air-stable short-channel polymer organic field-effect transistor (OFET) arrays with high saturated output current density are demonstrated by utilizing a novel solution-processed naphthobisthiadiazole (NTz) based donor–acceptor semiconducting polymer (PNTz4T) and designing a three-dimensional vertical channel structure with an extremely large ratio of channel width to channel length. The saturated mean field-effect mobility of 0.16cm2/Vs of the short-channel polymer devices remains over one month resulting in air-stable OFET arrays with high on/off ratio over 106 and powerful current–density exceeding 0.3A/cm2 under low operation voltage, both of which meet the requirements for such applications as driving organic light-emitting diodes in active-matrix displays.

Next Generation Non-Vacuum, Maskless, Low Temperature Nanoparticle Ink Laser Digital Direct Metal Patterning for a Large Area Flexible Electronics

Flexible electronics opened a new class of future electronics. The foldable, light and durable nature of flexible electronics allows vast flexibility in applications such as display, energy devices and mobile electronics. Even though conventional electronics fabrication methods are well developed for rigid substrates, direct application or slight modification of conventional processes for flexible electronics fabrication cannot work. The future flexible electronics fabrication requires totally new low-temperature process development optimized for flexible substrate and it should be based on new material too. Here we present a simple approach to developing a flexible electronics fabrication without using conventional vacuum deposition and photolithography. We found that direct metal patterning based on laser-induced local melting of metal nanoparticle ink is a promising low-temperature alternative to vacuum deposition– and photolithography-based conventional metal patterning processes. The “digital” nature of the proposed direct metal patterning process removes the need for expensive photomask and allows easy design modification and short turnaround time. This new process can be extremely useful for current small-volume, large-variety manufacturing paradigms. Besides, simple, scalable, fast and low-temperature processes can lead to cost-effective fabrication methods on a large-area polymer substrate. The developed process was successfully applied to demonstrate high-quality Ag patterning (2.1 µΩ·cm) and high-performance flexible organic field effect transistor arrays.

Solution-processed, Self-organized Organic Single Crystal Arrays with Controlled Crystal Orientation

A facile solution process for the fabrication of organic single crystal semiconductor devices which meets the demand for low-cost and large-area fabrication of high performance electronic devices is demonstrated. In this paper, we develop a bottom-up method which enables direct formation of organic semiconductor single crystals at selected locations with desired orientations. Here oriented growth of one-dimensional organic crystals is achieved by using self-assembly of organic molecules as the driving force to align these crystals in patterned regions. Based upon the self-organized organic single crystals, we fabricate organic field effect transistor arrays which exhibit an average field-effect mobility of 1.1 cm2V−1s−1. This method can be carried out under ambient atmosphere at room temperature, thus particularly promising for production of future plastic electronics.

Real-time vapour sensing using an OFET-based electronic nose and genetic programming

Electronic noses (e-noses) are increasingly being used as vapour sensors in a range of application areas. E-noses made up of arrays of organic field-effect transistors (OFETs) are particularly valuable due the range and diversity of the information which they provide concerning analyte binding. This study demonstrates that arrays of OFETs, when combined with a data analysis technique using Genetic Programming (GP), can selectively detect airborne analytes in real time. The use of multiple parameters – on resistance, off current and mobility – collected from multiple transistors coated with different semiconducting polymers gives dramatic improvements in the sensitivity (true positive rate), specificity (true negative rate) and speed of sensing. Computer-controlled data collection allows the identification of analytes in real-time, with a time-lag between exposure and detection of the order of 4 s.