Solid superionic RbAg4I5 electrolyte gated organic synaptic transistor

What is it about?

Herein, we have developed a superionic gate dielectric in combination with an inert polymer polyethylene oxide (PEO) and unusual isostructural solid electrolyte RbAg4I5 thin-film to operate an organic thin-film transistor (OTFT) at the ultralow voltages in a highly reproducible manner, which will also mimic various synaptic functions efficiently. Accordingly, we can name this device as the synaptic transistor (ST). Due to having colossal dielectric constant of the chosen superionic conductor RbAg4I5, the overall gate dielectric induces a very large specific capacitance that forces the ST to operate at very low voltages. Usually, RbAg4I5 displays an ionic conductivity of 0.2 (ohm.cm)-1 at room temperature, and this is entirely attributed to the presence of mobile silver ions. Most importantly, high dielectric constant also reduces the electronic leakage current significantly through the gate terminal at the time of synaptic activities related measurements and this property definitely improves the retention of high-conducting states. Another strong aspect of this approach is the stability of rubidium (Rb) against moisture and would be very effective to avoid the influence of environmental moisture.

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Photo by Hal Gatewood on Unsplash

Photo by Hal Gatewood on Unsplash

Why is it important?

• Solid superionic RbAg4I5 electrolyte gated organic synaptic transistor is fabricated and demonstrated high performance. In our perception, this electrolyte gating will be the first report in this category of transistor devices. • Our transistor successfully mimic various synaptic behaviors including EPSC, STP to LTP, STDP, and most importantly analogue like continuous tunable 2 × 103 discrete conducting states while maintaining energy consumption as low as 2.0 pJ per synaptic event. • We also achieved the On/Off current ratio higher than 105, bulk conductivity as high as 12 S/cm, and carrier mobility up to 0.25 cm2/Vs. • Bound state formation of electrons at the gate terminal under a negative bias stress with the mobile Ag+ ions into the PEO/RbAg4I5 dielectric layer and simultaneous formation of polarons through oxidation of P3HT unit into the channel is proposed as the basic working principle of this synaptic transistor.

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