Photoelectric Synaptic Devices Based On Copper(?) Phthalocyanine

Synapses are the basis of brain learning and memory,the development of artificial synaptic devices is the key to constructing neuromorphic computing system in physical level.For human beings,nearly 80%of the information is perceived through the visual system,so the development of synaptic devices with optical sensing is very important to simulate the human visual nervous system.Moreover,compared with electrical stimulation and electrical output artificial synaptic devices,optoelectronic synaptic devices are considered as one of the most promising candidates to replace the traditional von Neumann computing system due to the advantages of high bandwidth,ultra-fast signal transmission and low energy consumption.Organic semiconductors have the advantages of low cost,simple fabrication and flexible substrate combination.Thus,they are increasingly applied in the synaptic devices.In organic optoelectronic synaptic devices,how to reduce the recombination rate of photogenerated carriers in organic semiconductors is one of the most serious challenges.In this paper,three kinds of optoelectronic synaptic devices based on p-type organic semiconductor copper phthalocyanine(CuPc)are prepared,and combined with the organic ferroelectric material polyvinylidene fluoride-trifluoroethylene(P(VDF-Tr FE))to adjust the interface barrier,which improve the performance of the device.The main research contents are as follows:1.The two-terminal organic optoelectronic synaptic device based on ITO/PEDOT:PSS/P(VDF-Tr FE)/CuPc/Au was fabricated.The synaptic device responsed to 660 nm optical pulses sensitively.After applying five consecutive optical pulses,the photocurrent remained at 79% of its maximum value after 20 s.In contrast,ITO/PEDOT:PSS/CuPc/Au device attenuated the photocurrent to 56%of the maximum current after 20 s.It's obvious that the introduction of P(VDF-Tr FE)layer between the PEDOT:PSS and CuPc layers slows down the recombination of photocarriers,and improves retention characteristics.The optoelectronic device successfully simulates some important synaptic functions,as well as learning and experiential behaviors.Furthermore,the main characteristics of nociceptors and the human visual memory are simulated.2.A self-powered optoelectronic synaptic device based on ITO/P(VDF-Tr FE)/CuPc/F₁₆CuPc/Al was fabricated.The device exhibits inhibitory postsynaptic current(IPSC)when stimulated by 660 nm optical pulses.The device successfully simulates some important inhibitory synaptic functions.Due to the negative correlation between spike-dependent plasticity and frequency,the self-powered photonic synaptic device has the potential to perform dynamic low-pass filtering for image preprocessing and realize image blur processing.3.ITO/CuPc/P(VDF-Tr FE)/Au optoelectronic synaptic device was prepared.The two-terminal device shows increasing photocurrent responsed to the 660 nm optical pulse sequences,while has suppression effect at the 445 nm wavelength.This bidirectional response allows the device to simulate excitatory and inhibitory synaptic behavior under all-optical modulation.The introduction of the ferroelectric polymer P(VDF-Tr FE)creates a potential barrier between the organic semiconductor CuPc and Au electrode,which is favorable for the photocarriers to be captured by the defect,slows down the recombination,and greatly improves the retention characteristics of the device.In addition,the ferroelectric polarization of P(VDF-Tr FE)also affects the attenuation behavior of the response current of the device.In addition to simulating some basic functions of biological synapse,the function of nociceptor and pain inhibition process are successfully simulated via this device.