Low Voltage Organic Light-Emitting Synaptic Transistors for Neuromorphic In-Display Processing

Organic neuromorphic electronics using flexible organic semiconductors pave the way for the development of energy-efficient and intelligent devices, particularly in wearable applications. To create user-friendly systems, wearable neuromorphic devices need to provide outputs that are easily recognizable to user through light-emitting devices. The previous approach of employing external processing units to transmit signals from neuromorphic devices to display devices can give rise to limitations similar to those encountered in conventional electronic systems. Organic light-emitting synaptic transistors (OLESTs) offer a potential solution by integrating the functions of synaptic processing and light-emission in a single device. Despite this advantage, high voltage operation (&gt;30V) in previous light-emitting synaptic transistors remains a main challenge that requires further investigation and improvement.<br/>Here, we present low voltage OLESTs achieved through the electrochemical doping of semiconducting light-emitting polymers (LEPs). By utilizing surfactant molecules, we enhance the ion transport in the LEP channel, resulting in low turn on voltage (|<i>V</i>_DS|=2.0V at |<i>V</i>_GS|=1.0V that is lower than band gap of LEP (<i>E</i>g=2.17eV) due to spontaneous band bending during the OFF state. With the low switching and channel voltage (2.5V), the synaptic plasticity with luminescent outputs was demonstrated. Finally, we show neuromorphic in-display processing using a sensory neuromorphic display system. This system utilizes a hierarchical structure consisting of temperature sensor, spike generator, and OLEST to provide intuitive visible warning signals to patients suffering from sensory disabilities. Our results present a new approach for the realization of user-friendly neuromorphic display systems in intelligent wearable electronics.