A Light-Responsive Molecular Dielectric Surface for Ultraviolet-Selective Organic Optoelectronic Artificial Synapses

Abstract

Optoelectronic synapses, capable of perceiving and retaining external visual information, are ideally suited for the development of future biomimetic eyes and visual automation systems. Organic field-effect transistors (OFETs) have emerged as a powerful platform for artificial neuromorphic computing systems. However, intricate design and fabrication of devices are required to modulate the light-response ability and the charge transfer at the interface. In this study, we successfully fabricated a [1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-12) UV-sensitive synaptic transistor, exhibiting prominent visual synaptic behavior. This was achieved by functionalizing the dielectric layer with light-responsive azobenzene (AZO) derivatives through sequential reactions with silanes, significantly improving the performance of OFET-based synapses. By adjustment of the silane precursors and thus control of the number of AZO groups grafted on the interface, the light sensitivity of the as-fabricated photonic synapse is easily adjusted. The responsivity (R) and specific detectivity (D*) of these AZO-grafted OFET have reached as high as 23.9 A/W and 5.4 × 10¹⁰ cm Hz^0.5 W^–1. The superior UV sensitivity and synaptic behavior of the OFET with a densely grafted AZO interface stem from the efficient capture and retention of photogenerated electrons at defect sites, facilitated by the photoisomerization of AZO. Proof-of-concept demonstration by UV light pulses to simulate multiple brain activities, such as perception, processing, and memory of visual information, uncovers its potential in artificial intelligence and enlightens a research direction for developing neuromorphic devices.