Stochastic resonance in synapse-mimicking ferroelectric organic field-effect transistor

Ferroelectric organic field-effect transistors (FE-OFETs) are fabricated to implement the functions of a neural synapse, including one-directional signal transmission and synaptic plasticity. Stochastic resonance (SR) experiments are conducted with FE-OFETs that use regioregular poly(3-hexylthiophene-2,5-diyl) as the semiconductor layer and poly(vinylidene fluoride-co-hexafluoropropylene) as the insulator layer. The input–output correlation is observed to increase as the external noise intensity rises, with a cutoff frequency of 1 Hz, demonstrating the experimental occurrence of SR in the fabricated FE-OFETs. Furthermore, vibrational resonance experiments are performed to clarify the frequency-dependence of the SR behavior. The peak input–output correlation shifts toward higher amplitudes of a secondary sine wave that is applied instead of external noise as the frequency of the input signal rises from $f_{\text{signal}}$ = 0.5–1 Hz. The FE-OFETs exhibit more adaptive behavior than paraelectric OFETs, with a threshold voltage that changes dynamically according to the frequency characteristics of the input signal and/or external noise. Furthermore,the immediate response to abrupt environmental changes via the SR phenomenon and flexible behavior based on past experience via hysteresis effects can be implemented by a single FE-OFET element. (paper)