Organic phototransistors and their applications as artificial synapses

Sensors and Internet of Things (IoT) have been revolutionizing our world by establishing a smart and more sustainable environment. Low-temperature processing and chemical functionality of organic semiconductors, high-k of natural dielectric materials, and mechanically flexible substrates make organic field-effect transistor (OFET)-based sensors an attractive alternative in many fields which includes biomedical, security, environment, and neuromorphic computing technologies. One of the most striking application areas of OFETs is their use as artificial synapses. Indeed, several (opto)electronic field-effect devices have recently been proposed to simulate synaptic functions of the biological brain. OFETs offer excellent opportunities to replace the conventional von Neumann's computing systems. Among the sensor devices used to build artificial synapses, OFETs are one of the most promising candidates for neuromorphic computers and bioelectronics owing to their easy processing, flexible device configuration, mechanical bendability, low cost, biocompatibility, and ductility. As such, organic phototransistors (OPTs) have attracted tremendous attention due to their many advantages, namely the facile preparation process, easy integration, and tunable optoelectronic properties over various device configurations. Moreover, the use of OPTs to emulate the unique properties of biological synapses is regarded as the key to the advancements of artificial intelligence (AI). Herein, we first review the fabrication and operating mechanisms of OFETs and OPTs. The recent developments and applications of organic phototransistors as artificial synapses are thereafter described and discussed.