Neuromorphic Devices Based On Halide Perovskite

With the advent of"big data era",the problem of low efficiency and high energy consumption of traditional computer system is increasingly serious.One of the effective ways to solve this problem is to simulate the structure and working principle of human brain and develop brain-like neuromorphic devices to realize efficient,parallel and low-power computing.Halide perovskite has excellent optoelectronic properties and is widely used in neuromorphic devices as an electrical and optical active layer.In earlier studies,synaptic devices based on organic-inorganic hybrid halide perovskites were mainly focused on electrical stimulation.Compared with biological synapses,such devices still have some short-comings such as low bandwidth and high power consumption.Optoelectronic synapses stimulated by optical signals can combine optical sensing with synaptic functions.Making full use of the optoelectronic characteristics of halide perovskites to construct a neuromorphic device with photoelectric cooperation and integrated sensing and memory is one of the effective methods to reduce power consumption and improve information processing speed.Based on these questions,we mainly constructs neuromorphic devices based on organo-metal halide perovskite CH₃NH₃Pb I₃（MAPb I₃）and lead-free double perovskite Cs₂Ag Bi Br₆.We studies the optical and electrical characteristics of the devices,simulates synaptic behaviors and explores the mechanism.The specific research contents are as follows:1.In order to improve the photoelectric performance and stability of MAPb I₃ thin films,potassium iodide（KI）was introduced as an additive in the preparation of MAPb I₃film,and the two-terminal synaptic device based on KI-MAPb I₃ hybrid film is prepared.The KI used as an additive in the film preparation process greatly reduces grain boundaries,facilitating the improvement of device performance.The prepared synaptic device exhibits dual response to electric and light stimuli.The learning behavior of human under different moods and Pavlov’s dog experiment are also simulated by combining electronic and optical stimuli.For image recognition,the simulation result based on handwritten numerals（MNIST）dataset shows that the device achieves an accuracy of 84.2%under light illumination after only 1500 learning phases.2.The instability and toxicity of organic and inorganic hybrid perovskite restrict their further application in nonvolatile memory and artificial synaptic devices.Herein,a lead-free and air-stable memristor based on Cs₂Ag Bi Br₆is fabricated,which exhibits typical resistive switching（RS）characteristics and synaptic plasticity.The ion migration of Br^-and Ag⁺in Cs₂Ag Bi Br₆ led to the formation and fracture of a conductive filament.Notably,the device exhibits good environmental stability.Furthermore,the recognition rate reaches 91.3%by using the MNIST handwritten data set.3.Optoelectronic synapses can combine optical sensing with synaptic functions,which helps to broaden bandwidth,reduce interconnection energy consumption,and realize functional integration of sensing,memory and computing.Based on the excellent photoelectric performance of Cs₂Ag Bi Br₆,we prepared a self-powered optoelectronic synaptic device Au/P（VDF-Tr FE）/Cs₂Ag Bi Br₆/ITO based on Cs₂Ag Bi Br₆ and ferroelectric polymer P（VDF-Tr FE）.The device successfully simulated the synaptic functions such as PPF,SNDP and SRDP at 445 nm light pulses.Based on the synaptic plasticity of this device,a reservoir computing system is constructed,which greatly reduces the training cost in the network,and realizes the recognition of gray face image with an accuracy of 99.67%.This work provides a new way to realize ultra-low power machine vision using optoelectronic synaptic devices.4.Achieving potentiation and depression behavior under all-optical control based on a single device is an effective way to reduce electrical consumption.A self-powered two-terminal optoelectronic synapse based on a pentacene/P（VDF-Tr FE）/Cs₂Ag Bi Br₆heterostructure is designed,which shows bidirectional responses to optical stimuli with different wavelengths（λ=445 nm/660 nm）.This feature enables the device to emulate both excitatory and inhibitory synaptic behaviors in a fully optical pathway.Besides optical stimulus,humidity is used as additional stimulus to modulate the synaptic performance of the device under 445 nm illumination.The device is successfully applied to stimulate the behavior of the weather tree forecast and visual learning and forgetting processes under different mood states via humidity modulation.