Solution-Processed Synaptic Memristors Based on Halide Perovskite Nanocrystals

Abstract

Exploring new materials and structures to construct synaptic devices represents a promising route to fundamentally approach novel forms of computing. Nanocrystals (NCs) of halide perovskites possess unique charge transport characteristics, i.e., ionic−electronic coupling, holding considerable promise for energy-efficient and reconfigurable artificial synapses. Herein, we report solution-processed thin-film memristors from all-inorganic CsPbBr 3 perovskite NCs, functioning as an electrically programmable analog memory with good stability. The devices are demonstrated to successfully emulate a number of essential synaptic functions with low power consumption, including reversible potentiation and depression, short-term plasticity (STP), paired-pulse facilitation (PPF), and long-term plasticity (LTP), such as spike-number-dependent plasticity (SNDP), spike-rate-dependent plasticity (SRDP), spike-timing-dependent plasticity (STDP), and spike-voltage-dependent plasticity (SVDP). It is proposed that a coupled capacitive and inductive phenomenon originating from charge trapping and ion migration in CsPbBr 3 NC films, controlled by the amplitude and timing of the programming pulses, defines the degree of synaptic plasticity. A transition emerges from the fast traprelated capacitive regime to a slow ionic inductive regime, which enables continuous change of the film resistance and the magnitude of the electronic current, analogous to the synaptic weight modulation in biological synapses.

Long-term potentiation mechanism of biological postsynaptic activity in neuro-inspired halide perovskite memristors

“…Before we proceed any further, we should indicate that, in a previous paper [34], the authors obtained identical time transient responses to single-pulsing voltage perturbations, under certain conditions, by using a two-dimensional model and numerical simulations. Similarly, the dominant effect of the chemical inductor could be observed through the temporal evolution of the non-linear resistance in perovskite-based synaptic memristors, where the internal crossfire between charge trapping and ion migration also forms fascinating transient dynamics (with positive and negative spikes) that define the degree of artificial neuroplasticity [35].…”

Transient On/Off Photocurrent Response of Halide Perovskite Photodetectors

“…Otherwise, the current reaches the equilibrium value, as shown in Figure b. This increase of the current is the key property of perovskite synapses for neural networks that has already been characterized in terms of the inductive current. , …”

“…This increase of the current is the key property of perovskite synapses for neural networks that has already been characterized in terms of the inductive current. 32,60 Another phenomenon occurs when the voltage pulse is finished in which the current is inverted. This is because the internal u 1 cannot change instantaneously.…”

Size and Surface Chemistry Effects on the Synaptic Behavior of Halide Perovskite Thin Films

“…Together, they lead to reduced energy barrier and enhanced ion migration, and thereby a larger current enhancement by the pulse excitation. 6,18 Nevertheless, it should be pointed out that an increase of vacancy defect density usually leads to increased unintentional doping and the magnitude of film current which exposes a negative impact on the energy consumption of the device. 33 A previous study demonstrates that the incorporation of short alkyl ligands to the NC surface decreases the film conductance.…”

“…As one of the most intensively studied variants, perovskite nanocrystals (NCs) are also promising in artificial synapses due to their distinct electrical and optical properties compared to their bulk counterparts . Previously, Liu et al have shown the implementation of CsPbBr 3 NCs in memristors, emulating many essential synaptic functions with low power consumption . A unique coupled capacitive and inductive phenomenon caused by charge trapping and ion migration in perovskite-NC films is found to be responsible for defining the degree of synaptic plasticity.…”