New Chemical Dopant and Counterion Mechanism for Organic Electrochemical Transistors and Organic Mixed Ionic-Electronic Conductors

Synergistic effects in ambipolar blends of mixed ionic-electronic conductors

Organic mixed ionic-electronic conductors (OMIECs) are extensively utilized in bioelectronics, serving as essential components for converting biological signals into electronic ones. In the realm of ambipolar OMIECs, which support the transport of both electrons and holes, recent studies have introduced a novel blend approach to simplify fabrication and enhance tunability. However, these systems remain scarce, and the urge to advance blend-based OMIEC research is still emerging. Here, we present an extensive investigation of a polymer-fullerene ambipolar system, revealing the remarkable relationship between blend microstructure and system performance. Our results demonstrate that the capacitance and mobility of the blend components exhibit synergistic enhancements, surpassing the values observed in pristine materials. Additionally, the transient response time indicates a significant advantage for blends over pristine materials. These findings are elucidated through a schematic illustration of the blend morphology, providing profound insights into the properties of this system. This comprehensive study paves the way for the improved design of ambipolar OMIECs for use in bio-interfaces, advanced sensing applications, and innovative electronic devices.

Broadband THz Modulation via Solid-State Organic Electrochemical Devices

The sub-Terahertz and Terahertz bands play a critical role in next-generation wireless communication and sensing technologies, thanks to the large amount of available bandwidth in this spectral regime. While long-wavelength (microwave to mm-Wave) and short-wavelength (near-infrared to ultraviolet) devices are well-established and studied, the sub-THz to THz regime remains relatively underexplored and underutilized. Traditional approaches used in the aforementioned spectral regions are more difficult to replicate in the THz band, leading to the need for the development of novel devices and structures that can manipulate THz radiation effectively. Herein a novel organic, solid-state electrochemical device is presented, capable of achieving modulation depths of over 90% from ≈500 nm of a conducting polymer that switches conductivity over a large dynamic range upon application of an electronically controllable external bias. The stability of such devices under long-term, repeated voltage switching, as well as continuous biasing at a single voltage, is also explored. Switching stabilities and long-term bias stabilities are achieved over two days for both use cases. Additionally, both depletion mode (always "ON") and accumulation mode (always "OFF") operation are demonstrated. These results suggest applications of organic electrochemical THz modulators in large area and flexible implementations.

The Rising of Flexible Organic Electrochemical Transistors in Sensors and Intelligent Circuits

Flexible electronic devices in biomedicine, environmental monitoring, and brain-like computing have garnered significant attention. Among these, organic electrochemical transistors (OECTs) have been spotlighted in flexible sensors and neuromorphic circuits for their low power consumption, high signal amplification, excellent biocompatibility, chemical stability, stretchability, and flexibility. However, OECTs will also face some challenges on the way to commercialized applications, including the need for improved long-term stability, enhanced performance of N-type materials, integration with existing technologies, and cost-effective manufacturing processes. This review presents the device physics of OECTs in detail, including the evaluation of their various properties and the introduction of different configurations of the aforementioned OECTs. Subsequently, the components of this device and their roles are explained in depth, and the main ways to design and fabricate flexible OECTs are summarized. Following this, we summarize and analyze the principles and applications of OECTs for electrophysiological signal sensing, chemical sensing, biosensing, and sensor arrays. In addition, the concepts of OECT-based digital and neuromorphic circuits and their applications are presented. Finally, the paper summarizes the opportunities and challenges of OECT-based flexible electronics.

High-Hole-Mobility Fiber Organic Electrochemical Transistors for Next-Generation Adaptive Neuromorphic Bio-Hybrid Technologies

The latest developments in fiber design and materials science are paving the way for fibers to evolve from parts in passive components to functional parts in active fabrics. Designing conformable, organic electrochemical transistor (OECT) structures using poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) fibers has excellent potential for low-cost wearable bioelectronics, bio-hybrid devices, and adaptive neuromorphic technologies. However, to achieve high-performance, stable devices from PEDOT:PSS fibers, approaches are required to form electrodes on fibers with small diameters and poor wettability, that leads to irregular coatings. Additionally, PEDOT:PSS-fiber fabrication needs to move away from small batch processing to roll-to-roll or continuous processing. Here, it is shown that synergistic effects from a superior electrode/organic interface, and exceptional fiber alignment from continuous processing, enable PEDOT:PSS fiber-OECTs with stable contacts, high µC* product (1570.5 F cm-1 V-1 s-1 ), and high hole mobility over 45 cm2 V-1 s-1 . Fiber-electrochemical neuromorphic organic devices (fiber-ENODes) are developed to demonstrate that the high mobility fibers are promising building blocks for future bio-hybrid technologies. The fiber-ENODes demonstrate synaptic weight update in response to dopamine, as well as a form factor closely matching the neuronal axon terminal.