Self-powered optoelectronic artificial synapses based on a lead-free perovskite film for artificial visual perception systems

The visual perception system undertakes nearly 80% information perceiving tasks and its importance to human beings is self-evident. An optoelectronic synapse as the basic unit of artificial visual perception system not only incorporates photosensitive functions and synaptic plasticity, but also possesses the prospective advantages of high bandwidth, neglectable crosstalk and low-power dissipation. In this work, a two-terminal and self-powered optoelectronic synaptic device based on a 2D lead-free perovskite, Cs₃Bi₂Br₉, was fabricated. Upon optical stimulation, the device exhibits typical synaptic behaviors, including paired-pulse facilitation (PPF), transformation from short-term plasticity (STM) to long-term plasticity (LTM) and dynamic filtering via optical modulation. Furthermore, the optical stimulus-induced versatile criteria including threshold, relaxation, allodynia and hyperalgesia, of a nociceptor can be mimicked by the device under self-biased conditions. Such multifunctionality of the device could be put down to the unique optoelectronic properties of two-dimensional Cs₃Bi₂Br₉ and the interfacial trapping of dielectric poly(methyl methacrylate) layers. This work provides an energy-efficient approach for constructing retinal-neuromorphic systems.