An Artificial Optoelectronic Synapse Based on a Photoelectric Memcapacitor

DOI: 10.1002/aelm.201900858 away quickly when the light stimuli are removed.[3–5] In other words, traditional photodetectors can detect the images like a retina, but they lack the memory function owned by the visual cortex (see schematic illustration of human visual system in Figure 1a). To realize both detection and memory functions so as to better imitate the human visual system, researchers have attempted to integrate the photodetectors with the nonvolatile memory devices.[6–9] For example, a bioinspired visual system comprising an In2O3 nanowire photodetector connected in series with an Al2O3 memristor was fabricated recently, which could capture a butterflyshaped image and store it for more than 1 week.[9] In such integrated devices, however, the units responsible for detection, processing, and storage of optical information are physically separated, resulting in high power consumption for data transfer between different units (just as the Von Neumann bottleneck[10,11]). A simple yet effective humanoid optoelectronic device emerging recently is the artificial optoelectronic synapse based on the photoelectric memristor, which can co-locate the detection and memory functions in a single unit. As the name suggests, a photoelectric memristor can continuously change its resistance upon light stimuli, resembling the physiological The rapid development of artificial intelligence technology has led to the urge for artificial optoelectronic synapses with visual perception and memory capabilities. A new type of artificial optoelectronic synapse, namely a photo­ electric memcapacitor, is proposed and demonstrated. This photoelectric memcapacitor, with a planar Au/La1.875Sr0.125NiO4/Au metal–semiconductor– metal structure, displays a complementary optical and electrical modulation of capacitance, which can be attributed to the charge trapping/detrapping­ induced Schottky barrier variation. It further exhibits versatile synaptic functions, such as photonic potentiation/electric depression, paired­pulse facilitation, short­/long­term memory, and “learning­experience” behavior. Moreover, the photoplasticity of the memcapacitor can be modulated by varying the frequency of applied AC voltage, thus enabling self­adaptive optical signal detection and mimicry of interest­modulated human visual memory. Therefore, it represents a new paradigm for artificial optoelectronic synapses and opens up opportunities for developing low­power humanoid optoelectronic devices.