Tellurium-Vacancy Engineering in Ultrathin Bi2Te3 Enables Broadband Multifunctional Optoelectronic Synapse for Energy-Efficient Neuromorphic and Optical Information Processing.

Advances in optoelectronic synapses (OES) have relied on complex device configurations and fabrication processes, which limit their practical implementation. Here, we exploit the untapped potential of ultrathin Bi2Te3 to construct a multifunctional OES device for a range of applications in neuromorphic computing, biometric recognition, and artificial visual perception. The Te vacancies in the film trap and de-trap charges, leading to persistent photoconductivity as the operating mechanism. Specifically, we demonstrate successful defect engineering by controlling the annealing temperature of the Bi2Te3 films and directly correlate the OES performance with the defect density. The role of the Te vacancies in OES is further confirmed by first-principles calculations. The OES devices show excellent metrics such as 191.7% paired-pulse facilitation and 37.2 fJ per spike of energy consumption. The device successfully simulates Pavlov's classic associative learning experiment. A 6 × 6 device array, serving as an artificial retina for image processing, displays excellent retention of the learned optical information and memory performance by 57.4%. The OES devices demonstrate high accuracy in facial recognition (93.3%) and urban traffic scene segmentation (86.7%) tasks after 100 epochs. Finally, successful optical logic gate operations and Morse code for optical signal recognition and wireless communication are demonstrated using the OES devices.