Xanthan gum biopolymer gated low voltage-operating photo synaptic organic field-effect transistor for neuromorphic electronics

Low voltage-operating light-stimulated organic field-effect transistors (OFETs) are attracting huge attention due to their potential for developing photonic neuromorphic synapse-based neural networks resembling the human brain. The OFETs based on environment friendly biocompatible materials and processability are highly desired for realizing photo synaptic elements. In this report, we demonstrate a low voltage-operating Xanthan gum-gated poly(2,5-bis(3-alkylthiophen-2-yl) thieno[3,2-b] thiophene) [PBTTT-C14] based OFETs, exhibiting photo synaptic behavior at $-$0.3 V. The basic photo response parameters such as photoresponsivity, detectivity, and photocurrent to dark current ratio of the OFETs are estimated to quantify the photo synaptic behavior of the OFETs. We report the fundamental neurobiological characteristics such as excitatory post-synaptic current (EPSC), pair pulse facilitation (PPF), short-term plasticity (STP), long-term plasticity (LTP), learning-forgetting-memorizing (LFM), and conversion of STP to LTP for the Xanthan gum-gated PBTTT-C14-based OFETs. Furthermore, we showcase the electronic "OR" logic operations by employing the OFETs and replicate the Pavlovian conditioning experiment to mimic the associative learning phenomenon. Using these photo synaptic OFETs, we replicate human emotion and mood-swing-dependence learning and memory behavior which is an important aspect of cognitive learning. The OFETs exhibit fairly low energy consumption $\sim$100 pJ per optical operation to perform synaptic responses. We interpret and attribute the observed neuromorphic behavior to the charge-trapping occurring at the semiconductor-dielectric interface and bulk traps in OFETs. The presented results broaden opportunities to the device communities for building artificial complex neural networks using energy-efficient bio-polymer gated photo synaptic OFETs.