Flexible Transistors Research Articles

Development and Evaluation of Thread Transistor Based on Carbon-Nanotube Composite Thread with Ionic Gel and Its Application to Logic Gates

We propose a new type of flexible transistor based on carbon-nanotube (CNT) composite thread (CNTCT), i.e., a thread transistor, with ionic gel. In our previous study, we demonstrated that transistor operation was possible by combining metallic and semiconducting CNTCTs as gate and channel with an insulating material. However, its performance was not sufficient. Therefore, we here aim to improve it. For this, we tried to apply ionic gel as a dielectric layer to it. With this, the transistor was expected to be an electric-double-layer transistor. The transistor performance was improved, and the on/off ratio of the transistor increased by more than 4. This is a large value compared to our previous work. In addition, we not only evaluated the performance of the transistors, but also investigated whether they could be used as logic circuits. It was confirmed that the logic circuit composed of the thread transistor also operated correctly and stably for a long period of time. It was also confirmed that the output changed in response to weak external forces. These results indicate that it is a flexible transistor that can be used in a wide range of applications such as logic circuits and sensors.

Ultrasensitive Flexible Organic Synaptic Transistors Modulated by a Chemically Cross-Linked Solvent-Resistive Ion Composite.

We demonstrate a flexible organic synaptic transistor (FOST) with an ion-composite electrolyte film resistant to chemical reagents, which uses a three-dimensionally cross-linked polyimide matrix to accommodate a high-concentration ionic liquid. FOST shows versatile synaptic plasticity for classical conditioning, high-pass filtering, and the learning-forgetting process. The device achieves low-energy consumption down to 1.02 femtojoule per synaptic event with an ultrasensitive impulse to presynaptic spike down to 0.5 mV. Moreover, the electrical performance of the device is still stable after 1000 mechanical bending cycles. These results demonstrate that the device can be applied to future flexible neuromorphic electronics.

Van der Waals GeSe with Strain- and Gate-Tunable Linear Dichroism for Wearable Electronics.

The direct detection of light polarization poses a crucial challenge in the field of optoelectronics and photonics. Herein, the tunable linear dichroism (LD) in GeSe-based polarized photodetectors is presented through electronic and structural asymmetry modulation, and demonstrate their application prospects in wearable electronics. An improvement in the dichroic ratio up to 34% is achieved under a gate voltage of 20V, and the improvement reaches 44% by applying a tensile strain along the zigzag direction. Theoretical calculations reveal that the gate regulation of barrier height between GeSe and Au electrodes is responsible for the electrical-tunable LD, while the anisotropic optical absorption in response to strains leads to the strain-tunable LD. Moreover, flexible GeSe transistors are developed for wearable applications including motion sensors and glucose monitors. This study offers viable approaches for modulating the optical anisotropy of low-dimensional materials and emphasizes the versatility of van der Waals materials for practical applications in wearable electronic devices.

Flexible p-Type WSe2 Transistors with Alumina Top-Gate Dielectric.

Tungsten diselenide (WSe2) field-effect transistors (FETs) are promising for emerging electronics because of their tunable polarity, enabling complementary transistor technology, and their suitability for flexible electronics through material transfer. In this work, we demonstrate flexible p-type WSe2 FETs with absolute drain currents |ID| up to 7 μA/μm. We achieve this by fabricating flexible top-gated FETs with a combined WSe2 and metal contact transfer approach using WSe2 grown by metal-organic chemical vapor deposition on sapphire. Despite moderate WSe2 crystal grain size, our devices show similar or higher |ID| and ID on/off ratio (∼105) compared to most devices with exfoliated single-crystal WSe2 from the literature. We analyze charge trapping in our devices using pulsed and bias stress measurements. Notably, the high |ID| values are preserved during pulsing, where charge trapping is minimized. Overall, we demonstrate a fabrication approach advantageous for high drain currents in flexible 2D transistors.

IGZO/PVP Composite Nanofiber Neuromorphic Transistors with Optoelectronic Synapse Emulation and Reservoir Computing.

Nanofiber neuromorphic transistors are regarded as promising candidates for mimicking brain-like learning and advancing high-performance computing. Composite nanofibers (CNFs) typically exhibit enhanced optoelectronic and mechanical properties. In this study, indium-gallium-zinc oxide (IGZO)/polyvinylpyrrolidone (PVP) CNFs were synthesized, and the neuromorphic transistor was integrated on both rigid and flexible substrates. The learning behavior, characterized by the transition from short-term plasticity (STP) to long-term plasticity, was achieved through photoelectric stimulation of the rigid neuromorphic transistor. The nonlinear STP was simulated by the flexible neuromorphic transistor through electrical pulses, matching effectively with a reservoir computing (RC) system. Hand gesture recognition with little energy consumption (49 pJ per reservoir state) and a maximum accuracy of 92.86% has been achieved by the RC system, proving the substantial potential of the IGZO/PVP CNF neuromorphic transistor for wearable intelligent processing tasks.

Bioinspired Flexible and Low-Voltage Organic Synaptic Transistors for UV Light-Driven Vision Systems.

Neuromorphic vision systems, particularly those stimulated by ultraviolet (UV) light, hold great potential applications in portable electronics, wearable technology, biological analysis, military surveillance, etc. Organic artificial synaptic devices hold immense potential in this field due to their ease of processing, flexibility, and biocompatibility. In this work, we have fabricated a flexible organic field-effect transistor (OFET) that utilizes chitosan-silver nanoparticles (AgNPs) composite material as the active dielectric material. During UV light illumination, both silver nanoparticles and the pentacene layer generate a large number of charge carriers. The photogenerated carriers lead to a more significant hole accumulation at the pentacene interface, resulting in a current rise. In the absence of light, the trapped electron in the silver nanoparticles persists for a longer duration, preventing the instant recombination with holes. This extended retention of electrons leads to the observed synaptic performance of the transistor. The use of aluminum oxide (Al2O3) as one of the dielectric layers enables the device to operate effectively at low voltage (<1 V). The device mimics various crucial synaptic properties of the brain, including short-term potentiation and long-term potentiation (STP and LTP), paired-pulse facilitation (PPF), spike-duration dependent plasticity (SDDP), spike-number dependent plasticity (SNDP), and spike-rate dependent plasticity (SRDP), etc. This work introduces an approach to develop flexible organic synaptic transistors that operate efficiently at low voltages, paving the way toward high-performance, UV light-driven neuromorphic vision systems.

Biaxial Strain Transfer in Monolayer MoS2 and WSe2 Transistor Structures.

Monolayer transition metal dichalcogenides are intensely explored as active materials in 2D material-based devices due to their potential to overcome device size limitations, sub-nanometric thickness, and robust mechanical properties. Considering their large band gap sensitivity to mechanical strain, single-layered TMDs are well-suited for strain-engineered devices. While the impact of various types of mechanical strain on the properties of a variety of TMDs has been studied in the past, TMD-based devices have rarely been studied under mechanical deformations, with uniaxial strain being the most common one. Biaxial strain on the other hand, which is an important mode of deformation, remains scarcely studied as far as 2D material devices are concerned. Here, we study the strain transfer efficiency in MoS2- and WSe2-based flexible transistor structures under biaxial deformation. Utilizing Raman spectroscopy, we identify that strains as high as 0.55% can be efficiently and homogeneously transferred from the substrate to the material in the transistor channel. In particular, for the WSe2 transistors, we capture the strain dependence of the higher-order Raman modes and show that they are up to five times more sensitive compared to the first-order ones. Our work demonstrates Raman spectroscopy as a nondestructive probe for strain detection in 2D material-based flexible electronics and deepens our understanding of the strain transfer effects on 2D TMD devices.

Machine Learning-Assisted 3D Flexible Organic Transistor for High-Accuracy Metabolites Analysis and Other Clinical Applications

The integration of advanced diagnostic technologies in healthcare is crucial for enhancing the accuracy and efficiency of disease detection and management. This paper presents an innovative approach combining machine learning-assisted 3D flexible fiber-based organic transistor (FOT) sensors for high-accuracy metabolite analysis and potential diagnostic applications. Machine learning algorithms further enhance the analytical capabilities of FOT sensors by effectively processing complex data, identifying patterns, and predicting diagnostic outcomes with 100% high accuracy. We explore the fabrication and operational mechanisms of these transistors, the role of machine learning in metabolite analysis, and their potential clinical applications by analyzing practical human blood samples for hypernatremia syndrome. This synergy not only improves diagnostic precision but also holds potential for the development of personalized diagnostics, tailoring treatments for individual metabolic profiles.

Highly Stable Flexible Organic Electrochemical Transistors with Natural Rubber Latex Additives.

Organic electrochemical transistors (OECTs) have attracted considerable interest in the context of wearable and implantable biosensors due to their remarkable signal amplification combined with seamless integration into biological systems. These properties underlie OECTs' potential utility across a range of bioelectronic applications. One of the main challenges to their practical applications is the mechanical limitation of PEDOT:PSS, the most typical conductive polymer used as a channel layer, when the OECTs are applied to implantable and stretchable bioelectronics. In this work, we address this critical issue by employing natural rubber latex (NRL) as an additive in PEDOT:PSS to improve flexibility and stretchability of the OECT channels. Although the inclusion of NRL leads to a decrease in transconductance, mainly due to a reduced carrier mobility from 0.3 to 0.1 cm2/V·s, the OECTs maintain satisfactory transconductance, exceeding 5 mS. Furthermore, it is demonstrated that the OECTs exhibit excellent mechanical stability while maintaining their performance even after 100 repetitive bending cycles. This work, therefore, suggests that the NRL/PEDOT:PSS composite film can be deployed for wearable/implantable applications, where high mechanical stability is needed. This finding opens up new avenues for practical use of OECTs in more robust and versatile wearable and implantable biosensors.

Flexible Organic Electrochemical Transistor Based on Conjugated Conducting Polymers

— The use of organic electrochemical transistors (OECTs) based on conjugated polymers has gained significant recognition owing to their impressive performance, flexibility, ease of fabrication, and suitability for specific applications where solid-state transistors may not be efficiently employed. Key advantages of OECT technology, such as simple device architecture, robustness in ambient or aqueous environments, straightforward additive manufacturing processes, low operational voltage, and compatibility with flexible, rough, stretchable, and large-area substrates, underscore its significance in various applications. These applications span the sensing of glucose [1], bacteria [2], dopamine [3], DNA [4], lactate [5], cell activities [6], and electrophysiological signals [7]. Notably, the absence of the necessity for a reference electrode, a crucial feature for wearable and textile sensors compared to three electrode-based electrochemical sensors, stands out. In this context, we have fabricated a side-gated OECT on a flexible polyethylene terephthalate (PET) substrate through a scalable screen-printing process where the source, drain, and gate terminals are screen-printed using silver (Ag) conductive ink. The semiconducting channel material employed is polyethylene dioxythiophene: polystyrene sulfonate (PEDOT: PSS), which is spin-coated. Additionally, poly methyl methacrylate (PMMA) has been spin-coated to serve as the dielectric. The OECT operates by volumetric gating of the channel through a gel electrolyte containing poly sodium 4-styrene sulfonate (PSSna), enabling polarization of the gate and channel to induce charge accumulation or depletion, driven by the application of a gate-source voltage. The OECT device structure demonstrated switching from the "ON" to "OFF” state with the application of a positive gate voltage, indicating its functionality as a p-type depletion mode transistor. Additionally, the OECT displayed a transconductance (gm) of 6.25×10-4 A/V, mobility (µ) of 1.242×1010 cm2 /Vs, and a threshold voltage (Vth) of -0.39 V, with the on/off ratio being relatively low at 7.22. The repeatability was confirmed through the fabrication of three devices that exhibited nearly identical behavior. Furthermore, in pursuit of faster response time, lower operating voltage, and miniaturization, additional work involves downscaling the active area length to 100µm from the reported 4mm active area length. The fabrication method not only holds the capability for large-scale production with a high yield in a cost-effective manner but also opens up possibilities for applications requiring swift design changes and digitally enabled direct-write techniques. Future work emphasizes functionalizing the electrolyte used in OECT to detect biomolecules such as glucose, pH, and ion species. Thus, this research underscores the potential usability of fabricated OECTs in various high-performance chemical and biological sensing applications. REFERENCES Tang, H.; Yan, F.; Lin, P.; Xu, J.; Chan, H.L.W. Highly Sensitive Glucose Biosensors Based on OrganicElectrochemical Transistors Using Platinum Gate Electrodes Modified with Enzyme and Nanomaterials.Adv. Funct. Mater. 2011, 21, 2264–2272. [CrossRef]He, R.-X.; Zhang, M.; Tan, F.; Leung, P.H.M.; Zhao, X.-Z.; Chan, H.L.W.; Yang, M.; Yan, F. Detection of bacteria with organic electrochemical transistors. J. Mater. Chem. 2012, 22, 22072–22076. [CrossRef]Gualandi, I.; Tonelli, D.; Mariani, F.; Scavetta, E.; Marzocchi, M.; Fraboni, B. Selective detection of dopamine with an all PEDOT:PSS Organic Electrochemical Transistor. Sci. Rep. 2016, 6, 35419. [CrossRef]Tao, W.; Lin, P.; Hu, J.; Ke, S.; Song, J.; Zeng, X. A sensitive DNA sensor based on an organic electrochemical transistor using a peptide nucleic acid-modified nanoporous gold gate electrode. RSC Adv. 2017, 7, 52118–52124. [CrossRef]Braendlein, M.; Pappa, A.-M.; Ferro, M.; Lopresti, A.; Acquaviva, C.; Mamessier, E.; Malliaras, G.G. Owens, R.M. Lactate Detection in Tumor Cell Cultures Using Organic Transistor Circuits. Adv. Mater. 2017, 1605744.Lin, P.; Yan, F.; Yu, J.; Chan, H.L.W.; Yang, M. The Application of Organic Electrochemical Transistors in Cell-Based Biosensors. Adv. Mater. 2010, 22, 3655–3660Liang, Y.; Ernst, M.; Brings, F.; Kireev, D.; Maybeck, V.; Offenhäusser, A.; Mayer, D. High Performance Flexible Organic Electrochemical Transistors for Monitoring Cardiac Action Potential. Adv. Healthc. Mater. 2018, 1800304. [CrossRef] Figure 1

Artificial optoelectronic synapses based on flexible and transparent oxide transistors

The development of artificial optoelectronic synapses utilizing flexible, and transparent oxide transistors is crucial for advancing neuromorphic computing and wearable electronics. Here, we propose artificial optoelectronic synapses on flexible and transparent devices based on an ion-gel gated oxide transistor. The device consists of indium-tin-oxide/ion-gel thin film conformity fabricated on a polyethylene terephthalate substrate. The device exhibited a loop opening in current–voltage properties, and its operating mechanism was ascribed to charge trapping and de-trapping. The neuromorphic behaviors can also be simulated by this device for instance, namely ultraviolet (UV) induced short-term memory, long-term memory, paired-pulse facilitation, and learning/forgetting behaviors. Additionally, electrical habituation and UV potentiation were executed. This work paves the way for the realization of low-cost flexible and transparent synaptic wearable electronics.

Flexible Organic Electrochemical Transistors for Energy-Efficient Neuromorphic Computing.

Brain-inspired flexible neuromorphic devices are of great significance for next-generation high-efficiency wearable sensing and computing systems. In this paper, we propose a flexible organic electrochemical transistor using poly[(bithiophene)-alternate-(2,5-di(2-octyldodecyl)- 3,6-di(thienyl)-pyrrolyl pyrrolidone)] (DPPT-TT) as the organic semiconductor and poly(methyl methacrylate) (PMMA)/LiClO4 solid-state electrolyte as the gate dielectric layer. Under gate voltage modulation, an electric double layer (EDL) forms between the dielectric layer and the channel, allowing the device to operate at low voltages. Furthermore, by leveraging the double layer effect and electrochemical doping within the device, we successfully mimic various synaptic behaviors, including excitatory post-synaptic currents (EPSC), paired-pulse facilitation (PPF), high-pass filtering characteristics, transitions from short-term plasticity (STP) to long-term plasticity (LTP), and demonstrate its image recognition and storage capabilities in a 3 × 3 array. Importantly, the device's electrical performance remains stable even after bending, achieving ultra-low-power consumption of 2.08 fJ per synaptic event at -0.001 V. This research may contribute to the development of ultra-low-power neuromorphic computing, biomimetic robotics, and artificial intelligence.

Induction of Synaptic Plasticity in Flexible Organic Synaptic Transistors with Cross‐Linked Polymer Dielectric

AbstractControlled cross‐linking of polymer dielectric poly (4‐vinylphenol) (PVP) is demonstrated as an effective tool in enhancing the performance of flexible organic synaptic transistors (OSTs). Investigation of variation of concentration of the cross‐linking agent methylated poly (melamine‐co‐formaldehyde) (PMCF) in PVP in bilayer combination with high‐k hafnium oxide (HfO2) as gate dielectric in devices shows that the lower concentration of cross‐linking agent results in better memory performance. OSTs with 26% PMCF concentration in PVP (by mass) exhibit excellent memory performance with memory window &gt; 4 V for VGS sweep of ±5 V, static retention of ≈104 s, dynamic retention for 500 cycles, and ≈125 continuous program/erase cycles. Pulse paired facilitation with relaxation time constants of 370 and 4670 ms respectively for slow and rapid phases with regulating modulation amplitude of ≈1 resemble a biological synapse. Through excitatory post synaptic current characteristics, spike timing dependant plasticity and spike voltage dependant plasticity are clearly observed, with low energy consumption per spike on the order of 10 pJ. Further, by leveraging the intricate interconnected data transfer and computation phenomenon, “AND” logic is effectively implemented using these OSTs. These exciting results may open up new directions toward the development of hardware for neuromorphic computing.

Flexible Solid-Electrolyte-Gated-Dielectric Carbon Nanotube Thin Film Transistors and Integrated Circuits with the Recorded Radiation Tolerance and Reparability.

Radiation-tolerance and repairable flexible transistors and integrated circuits (ICs) with low power consumption have become hot topics due to their wide applications in outer space, nuclear power plants, and X-ray imaging. Here, we designed and developed novel flexible semiconducting single-walled carbon nanotube (sc-SWCNT) thin-film transistors (TFTs) and ICs. Sc-SWCNT solid-electrolyte-gate dielectric (SEGD) TFTs showcase symmetric ambipolar characteristics with flat-band voltages (VFB) of ∼0 V, high ION/IOFF ratios (>105), and the recorded irradiation resistance (up to 22 Mrad). Moreover, flexible sc-SWCNT ICs, including CMOS-like inverters and NAND and NOR logic gates, have excellent operating characteristics with low power consumption (≤8.4 pW) and excellent irradiation resistance. Significantly, sc-SWCNT SEGD TFTs and ICs after radiation with a total irradiation dose (TID) ≥ 11 Mrad can be repaired after thermal heating at 100 °C. These outstanding characteristics are attributed to the designed device structures and key core materials including SEGD and sc-SWCNT.

A bioinspired neuromuscular system enabled by flexible electro-optical N2200 nanowire synaptic transistor

Mimicking the functional traits of the muscle system evolves the development of the neuromorphic prosthetic limbs. Herein, a bioinspired neuromuscular system was constructed by connecting an information processor that uses a flexible electro-optical synaptic transistor (FNST) to an effector that uses artificial muscle fibers. In this system, the response of artificial muscle fibers, which imitate the movement of biological muscle fibers, is manipulated by neuromorphic synaptic devices. The FNST is regulated by light pulses and electrical spikes to emulate biological synaptic functions, and thereby applied in secure communication. The feasibility of n-type organic nanowires acting as the channels for neuromorphic devices was demonstrated. Attributing to the flexibility of the n-type organic semiconductor N2200 nanowires, the current of the FNST retains >85% of its initial value after the 5000 bending cycles to radius = 1 cm. The tolerance of bending of the FNST implies its potential applications in wearable electronics. This work offers an approach to potentially advancing electronic skin, neuro-controlled robots, and neuromorphic prosthetic limbs.

스프레이 프린팅된 1 V 이하의 유연한 전해질 게이트 인버터

We demonstrate all-printed, low-voltage, and flexible electrolyte-gated transistors and inverters prepared through a facile spray-printing process. All active components of the electronic circuits, including source/drain electrodes, semiconductor, gate dielectric, gate electrode, and load resistor, were directly deposited via spray printing. The sprayed transistors show a high on/off ratio of ∼104. The printed devices also show excellent operational stability under successive bending stresses, maintaining 88% of their performance after 5,000 bending cycles at a small bending radius of 2 mm. Furthermore, the resistor-loaded flexible inverters exhibit appropriate rail-to-rail voltage inverting characteristics with a high voltage gain of ~9 at a low supply voltage of −1 V. These results demonstrate that the high-throughput strategy is promising for generating low-voltage, flexible, and all-spray-printed electronic circuits.

Two-step process for the fabrication of direct FLG\\MoS2 heterostructures

MoS2 has proven its efficacy in flexible electronics, transistor devices, and various biological and chemical applications. However, it is still challenging to achieve large-area MoS2 monolayers with desired material quality and electrical properties to fulfill the requirement for practical applications. Moreover, the main strategy for the preparation of a 2D heterostructure it is based on the sequential stacking of the layered materials using wet or dry transfer methods which introduces many defects. This paper presents an economically viable and straightforward two-step methodology to obtain MoS2 thin films, encompassing magnetron sputtering deposition of Mo and subsequent annealing in a sulfur-rich environment. This approach successfully yielded MoS2 thin films on Si\\SiO2 substrates. Additionally, heterostructures consisting of few layer graphene (FLG) and MoS2 were directly obtained using the same method. The utilization of grazing incidence X-ray diffraction verified the formation of the hexagonal MoS2 phase, a finding further confirmed by Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) investigations revealed the successful sulfurization process, with surface-bound oxides forming only subsequent to air exposure. Comprehensive assessment involving X-ray reflectivity, atomic force microscopy and XPS collectively inferred the fabrication of thin films comprised of a small number of MoS2 layers covering the entire substrate. Electrical assessments exhibited an electrical hysteresis, demonstrating its potential for memristor applications. Overall, this study outlines a cost-effective fabrication method for producing nanoscale MoS2 thin films with excellent properties, avoiding the use of toxic gases such as H2S. These findings contribute to the potential development of cutting-edge applications.

High mobility graphene field effect transistors on flexible EVA/PET foils

Monolayer graphene is a promising material for a wide range of applications, including sensors, optoelectronics, antennas, EMR shielding, flexible electronics, and conducting electrodes. Chemical vapor deposition (CVD) of carbon atoms on a metal catalyst is the most scalable and cost-efficient method for synthesizing high-quality, large-area monolayer graphene. The usual method of transferring the CVD graphene from the catalyst to a target substrate involves a polymer carrier which is dissolved after the transfer process is completed. Due to often unavoidable damage to graphene, as well as contamination and residues, carrier mobilities are typically 1000–3000 cm2(Vs)−1 , unless complex and elaborate measures are taken. Here, we report on a simple scalable fabrication method for flexible graphene field-effect transistors that eliminates the polymer interim carrier, by laminating the graphene directly onto office lamination foils, removing the catalyst, and depositing Parylene N as a gate dielectric and encapsulation layer. The fabricated transistors show field- and Hall-effect mobilities of 7000–10 000 cm2(Vs)−1 with a residual charge-carrier density of 2×1011 1 cm−2 at room temperature. We further validate the material quality by terahertz time-domain spectroscopy and observation of the quantum Hall effect at low temperatures in a moderate magnetic field of ∼5 T. The Parylene encapsulation provides long-term stability and protection against additional lithography steps, enabling vertical device integration in multilayer electronics on a flexible platform.

Aerosol Doping System for Microscale Seamless p-n Patterning of Carbon Nanotube Films.

Carbon nanotube (CNT) films are extensively researched as a promising material for wearable thermoelectric generators (TEGs) owing to their good flexibility and high thermoelectric conversion ability. Miniaturizing a pair of p- and n-type thermocouples and increasing the number of repeating elements can effectively increase the power of TEGs. However, conventional p-n patterning methods, such as dipping and printing, have a coarse resolution at the submillimeter level, thereby limiting the miniaturization rate. This study developed an aerosol doping system as a fine n-doping method. A dopant aerosol with a <3 μm diameter was formed through ultrasonic nebulization and air separation, while n-doping was achieved by exposing the CNT film to the dopant aerosol. Microscale p-n patterning of 1 μm was achieved through exposure using small-sized aerosols at an exceptionally slow rate of 3 Å/min. This resolution is 100 times higher than those of conventional p-n patterning methods. The developed aerosol doping system for CNTs can also be used on organic semiconductor materials, such as PEDOT/PSS and perovskite materials. Therefore, it has the potential to significantly impact the realization of Internet of Things (IoT) terminals, such as flexible TEGs, transistors, and solar cells.

Flexible Organic Electrochemical Transistor Based on Conjugated Conducting Polymers

In this work, we have fabricated a side-gated organic electrochemical transistor (OECT) where the source, drain, and gate terminals are screen-printed on a flexible polyethylene terephthalate substrate through a scalable screen-printing process. The semiconducting channel material is made of polyethylene dioxythiophene: polystyrene sulfonate (PEDOT: PSS), applied via spray coating. The OECT operates by volumetric gating of the channel through a gel electrolyte containing poly sodium 4-styrene sulfonate, transitioning highly conductive PEDOT+ to PEDOT0 through de-doping, biased by a positive gate voltage. Additionally, the OECT displayed a transconductance (gm) of 62.5 µA/V, mobility (µ) of 6.6×106 cm2 / Vs, and a threshold voltage (Vth) of -0.39 V, with the ON/OFF ratio being relatively low at 33.2. The repeatability was confirmed through the fabrication of three devices that exhibited nearly identical behavior. Future work emphasizes functionalizing the electrolyte to detect biomolecules such as glucose, pH, and ion species.