Influence of Molecular Weight of Polymer Electret on the Synaptic Organic Field‐Effect Transistor Performance

Abstract

Chargeable polymer electret‐based organic field‐effect transistor (OFET) memory devices are attractive for intrinsically flexible artificial synapse. However, the effects of molecular weight (Mw) of polymer electret on the charge trapping properties, especially the implementation of synaptic functions, are not yet well‐understood. In this work, the authors study pentacene‐based synaptic OFET memory made from two different molecular weight polymer electrets, with poly(N‐vinylcarbazole) (PVK) as the case study. Utilizing the synergistic effect of smooth surface morphology, higher polymer chain‐end density and lower dielectric constant, OFET memory device with lower Mw PVK electret showed a larger memory window (28.2 V) and faster write speed (1 ms) compared to that with higher Mw PVK. Benefiting from its charge‐trapping ability, the synaptic OFETs with lower Mw PVK delivered a better modulation of synaptic weight. The co‐modulation of photonic and electric operations enabled the reconfigurable short‐term plasticity and long‐term plasticity (LTP) in lower Mw PVK devices, further leading to the STP‐based emulation of visible color recognition and LTP‐based neural network simulation. This work enlightens a detailed understanding of the molecular weight‐dependent charge trapping behavior for the future integration of visible information sensing‐memory‐processing in optoelectronic OFET memory.

Flexible Floating-Gate Electric-Double-Layer Organic Transistor for Neuromorphic Computing

“…The conductance modulation was characterized by manipulating the pulse stimulation to the gate electrode and recording the drain current where the increase (decrease) of conductance refers to a synaptic potentiation (depression) behavior. Charge trapping and ion migration based synaptic transistors show an opposite hysteresis loop direction in the transfer curve; for the p-type synaptic transistor, the hysteresis loop direction is counterclockwise (source-drain current decrease) in terms of the charge trapping effect, whereas the hysteresis loop direction is clockwise (source-drain current increase) in terms of EDL effect . The memory window in the transfer curves could be used not only to help identify the charge trapping or ion migration but also to analyze the charge capture ability or ion migration ability in a quantitative manner.…”

Retina-inspired controllable neuromorphic vision organic sensors with ultraweak ultraviolet detection

“…The detailed explanation was described in Supplementary Note 1. And for the latter part, to demonstrate the advantage in image recognition with the pre-processing feature of focusing on UV information, a multi-layer perceptron-based ANN (400 input neurons, 100 hidden neurons and 10 output neurons) was simulated for image recognition 50 . During the image recognition, the Mixed National Institute of Standards and Technology (MNIST) handwritten image dataset was firstly used to train the ANN.…”

A brief review on device operations and working mechanisms of organic transistor photomemories

“…121 Last but not least, the development of polymer-based photosynaptic transistors keeps pace with other potential materials. 122,130,131,134 In this scope, a photosynaptic transistor utilizing P3HT- b -P2VP block copolymer active layer could emulate PPF, STDP/SRDP, and STP/LTP behaviors. 130 The corresponding LTM can keep the current contrast to 10 5 , the STM with a high PPF ratio of 1.38, and an ultralow energy consumption calculated ca.…”

“…131 The device contains of P3HT as active channel and CYTOP as a modifying layer for the dielectric surface with DEPSC values recorded up to 6.2 nA under the exertion of a single light pulse intensity of 0.15 mW cm À2 and duration of 4 s. And the very recent progress on photosynaptic device that using the same concept of photo-assisted operations (see in subsection of 4.4), while investigating the effect of molecular weight (Mw) of polymer electret to the photosynaptic behavior have been reported. 134 With poly(N-vinylcarbazole) (PVK) as the case study, such device could exhibit a larger memory window (28.2 V) bundling with an instantaneous programming speed of 1 ms for lower Mw PVK electret. The photosynaptic behaviors such as EPSC/IPSC, PPF/PPD, excellent tunability between STP and LTP, including high accuracy and STP-based RGB color recognition ability that could be further emulated on lower Mw PVK device by photo-assisted operations.…”