An Evolvable Organic Electrochemical Transistor for Neuromorphic Applications

Gerasimov, Jennifer Y.; Gabrielsson, Roger; Forchheimer, Robert; Stavrinidou, Eleni; Simon, Daniel T.; Berggren, Magnus; Fabiano, Simone

doi:10.1002/advs.201801339

Cited by 169 publications

(189 citation statements)

References 26 publications

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“…Another type of organic transistor, the organic electrochemical transistor (OECT), has recently established itself as a useful tool for emergent bioelectronic applications, brain and body implants, sensors, signal recorders, and neuromorphic systems . OECTs are governed by mixed ionic‐ and electronic‐conductivity, with high transconductance ( g m ) being an essential OECT parameter, characteristic of efficient ionic‐to‐electronic signal conversion .…”

Section: A Summary Of the Dispersive And Polar Surface Energy Componementioning

confidence: 99%

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

et al. 2019

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Contact resistance is renowned for its unfavorable impact on transistor performance. Despite its notoriety, the nature of contact resistance in organic electrochemical transistors (OECTs) remains unclear. Here, by investigating the role of contact resistance in n‐type OECTs, the first demonstration of source/drain‐electrode surface modification for achieving state‐of‐the‐art n‐type OECTs is reported. Specifically, thiol‐based self‐assembled monolayers (SAMs), 4‐methylbenzenethiol (MBT) and pentafluorobenzenethiol (PFBT), are used to investigate contact resistance in n‐type accumulation‐mode OECTs made from the hydrophilic copolymer P‐90, where the deliberate functionalization of the gold source/drain electrodes decreases and increases the energetic mismatch at the electrode/semiconductor interface, respectively. Although MBT treatment is found to increase the transconductance three‐fold, contact resistance is not found to be the dominant factor governing OECT performance. Additional morphology and surface energy investigations show that increased performance comes from SAM‐enhanced source/drain electrode surface energy, which improves wetting, semiconductor/metal interface quality, and semiconductor morphology at the electrode and channel. Overall, contact resistance in n‐type OECTs is investigated, whilst identifying source/drain electrode treatment as a useful device engineering strategy for achieving state of the art n‐type OECTs.

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Section: A Summary Of the Dispersive And Polar Surface Energy Componementioning

confidence: 99%

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

et al. 2019

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“…The concept of synchronization or similar neuroinspired functions may add in the future more biologically plausible features in neuromorphic device architectures beyond the well‐established neuroplasticity forms. At the device or architecture level, similar global oscillations G could be used in an array of electrochemical memory devices in order to collectively modulate the threshold of memory and thereby change the long‐term memory state only in specific phases of G by using additional local inputs I x,y . In this way, phase‐dependent learning/training features can be introduced in analogy with attention during biological learning processes.…”

Section: Discussionmentioning

confidence: 99%

Functional Connectivity of Organic Neuromorphic Devices by Global Voltage Oscillations

Koutsouras

Prodromakis

Malliaras

et al. 2019

Advanced Intelligent Systems

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Global oscillations in the brain synchronize neural populations and lead to dynamic binding between different regions. This functional connectivity reconfigures as needed for the architecture of the neural network, thereby transcending the limitations of its hardwired structure. Despite the fact that it underlies the versatility of biological computational systems, this concept is not captured in current neuromorphic device architectures. Herein, functional connectivity in an array of organic neuromorphic devices connected through an electrolyte is demonstrated. The output of these devices is shown to be synchronized by a global oscillatory input despite the fact that individual inputs are stochastic and independent. This temporal coupling is induced at a specific phase of the global oscillation in a way that is reminiscent of phase locking of neurons to brain oscillations. This demonstration provides a pathway toward new neuromorphic architectural paradigms, where dynamic binding transcends the limitations of structural connectivity, and could enable architectural concepts of hierarchical information flow.

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“…In the second case, EDL can also be formed, but the semiconductors are permeable to ions in the electrolyte, which can further dope and modulate the channel conductance in a nonvolatile way. In recent years, utilizing EGTs to mimic synaptic functions has emerged as a new research direction . The migration of ions in the electrolyte under the applied electric field is very similar to the release of neurotransmitters in response to an action potential .…”

Section: Electrolyte‐gate Synaptic Transistorsmentioning

confidence: 99%

Recent Advances in Transistor‐Based Artificial Synapses

Dai

Zhao

Wang

et al. 2019

Adv Funct Materials

474

422

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Simulating biological synapses with electronic devices is a re-emerging field of research. It is widely recognized as the first step in hardware building brain-like computers and artificial intelligent systems. Thus far, different types of electronic devices have been proposed to mimic synaptic functions. Among them, transistor-based artificial synapses have the advantages of good stability, relatively controllable testing parameters, clear operation mechanism, and can be constructed from a variety of materials. In addition, they can perform concurrent learning, in which synaptic weight update can be performed without interrupting the signal transmission process. Synergistic control of one device can also be implemented in a transistor-based artificial synapse, which opens up the possibility of developing robust neuron networks with significantly fewer neural elements. These unique features of transistor-based artificial synapses make them more suitable for emulating synaptic functions than other types of devices. However, the development of transistor-based artificial synapses is still in its very early stages. Herein, this article presents a review of recent advances in transistor-based artificial synapses in order to give a guideline for future implementation of synaptic functions with transistors. The main challenges and research directions of transistor-based artificial synapses are also presented.In the nerve system, a synapse is a specialized structure that allows a neuron to pass chemical or electrical signals to another Figure 2. a) Schematic illustration (top) and microscopy image (bottom) of flexible synaptic transistors based on a random matrix of semiconducting CNTs. b) Case 1: the amplitudes of V LTP and V LTP are greater than other cases; thus, NL is the highest and ΔG is the largest. c) Case 2: the amplitudes of V LTP and V LTP are smaller than in case 1; thus, NL and ΔG are lower. d) Case 3: if the CNT transistor without the Au floating gate is used for the synaptic transistor, NL and ΔG are considerably smaller than in the other cases due to the limited charge storage space. Reproduced with permission. [87]

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An Evolvable Organic Electrochemical Transistor for Neuromorphic Applications

Cited by 169 publications

References 26 publications

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

Functional Connectivity of Organic Neuromorphic Devices by Global Voltage Oscillations

Recent Advances in Transistor‐Based Artificial Synapses

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