Solution‐processed lead halide perovskites are considered one of the promising materials for flexible optoelectronics. However, the array integration of ultrathin flexible perovskite photodetectors (PDs) remains a significant challenge limited by the incompatibility of perovskite materials with manufacturing techniques involving polar liquids. Here, an ultrathin (2.4 µm) and conformable perovskite‐based PD array (10 × 10 pixels) with ultralight weight (3.12 g m−2) and excellent flexibility, is reported. Patterned all‐inorganic CsPbBr3 perovskite films with precise pixel position, controllable morphology, and homogenous dimension, are synthesized by a vacuum‐assisted drop‐casting patterning process as the active layer. The use of waterproof parylene‐C film as substrate and encapsulation layer effectively protects the perovskite films against penetration of polar liquids during the peeling‐off process. Benefitting from the encapsulation and ultrathin property, the device exhibits long‐term stability in the ambient environment, and robust mechanical stability under bending or 50% compressive strain. More importantly, the ultrathin flexible PD arrays conforming to hemispherical support realize imaging of light distribution, indicating the potential applications in retina‐like vision sensing.

The human visual system undertakes most of the information perceiving tasks, and nearly 80% of the perceived information is obtained via the visual system. The basic functions of the human visual system can be emulated by neuromorphic visual‐perception systems in the light region from UV to near‐IR. An optoelectronic synapse served as the basic unit of the neuromorphic visual‐perception system is required to combine photosensing function and synaptic element. In addition, optoelectronic synapses demonstrate the prospective advantage of large bandwidth, ultrafast signal transmission, and low electrical energy loss, which is expected in the photonic signal‐triggered computing. This work reviews recent progress in the optoelectrical synapses. Device architectures and working mechanisms are discussed. The applications in the artificial visual‐perception system for image memorization and pattern recognition are reviewed. The main challenges and opportunities of optoelectrical synapses are also presented.

energy consumption and inherent speed limitations. Inspired by human neural system, communicating through synapses with the features of parallel distributed processing and integrated storage and computation, various neuromorphic devices including memristors and fieldeffect transistors have been employed to simulate synaptic functions to overcome the von Neumann bottleneck. [1][2][3] Synaptic plasticity such as long/short-term potentiation (LTP/STP), long/short-term depression (LTD/STD), and paired pulse facilitation/depression (PPF/PPD), have been mimicked by modulating device conductivity (i.e., synaptic weight). Among these synaptic devices, potentiation and depression are always triggered by electrical stimulation. As known the electronic technology suffers the problem of limited computing speed because of the bandwidth connection density trade-off. [4] Fortunately, optoelectronic synapses with the light stimuli exhibit potential for ultrafast computing with advantages of the low crosstalk, high bandwidth, and low power consumption, also can be applied in optical wireless communication. [5,6] Herein, the optoelectronic synapses are operated with direct light illumination and the output is interpreted from the change of electrical conductance. It is different from the photonic devices that are mentioned in the photonic integrated circuits, in which the light is illuminated through a waveguide and output is denoted by the transmittance/absorbance of light in the waveguide. [7,8] However, most of reported optoelectronic devices only show positive photoresponse corresponding to the potentiation behavior of synapses. The achievement of depression behavior still depends on electrical stimulation due to the unidirectional photoresponse of devices. Therefore, a device with bidirectional photoresponse to emulate both excitatory and inhibitory behaviors for a fully optical-controlled artificial synapse is highly desired.Recently, a few of fully optical-controlled artificial synapses have been reported, such as pyrenyl graphdiyne/graphene/ PbS heterostructure, [5] Bi 2 O 2 Se/graphene hybrid structure, [6] ZnO/PbS hybrid heterostructure, [9] oxygen-deficient/oxygenrich InGaZnO homojunction, and black phosphorus. [10][11][12][13] Both the excitatory and inhibitory synaptic behaviors of Compared with electrical synapses, optoelectronic synapses exhibit great potential for ultrafast computing and wireless communication in neuromorphic hardware with advantages of low crosstalk, high bandwidth, and low power consumption. However, due to the unidirectional photoresponse in most of optoelectronic synapses, the related researches still focus on the electrical stimulation of inhibitory behaviors. Herein, a synaptic device based on perovskite−ZnO heterostructure is prepared with the characteristic of bidirectional photoresponse and can realize both the potentiation and depression by ultraviolet (UV) and green light stimuli, respectively. Consecutive UV and green light stimuli for potentiation and depression reveal the reliability ...