Dimensionality Dependent Plasticity in Halide Perovskite Artificial Synapses for Neuromorphic Computing

Abstract

properties of biological synapses and perform parallel operations, they require larger energy than a biological synapse. Therefore, development of an artificial synapse with energy consumption on the level of a biological synapse remains an open problem.Organic-inorganic halide perovskite (OHPs) may provide a material to solve this problem, because of their low activation energy of ion migration. Moreover, various structural modulation of polycrystalline films is possible with facile solution processing so that organic parts in the OHPs can control the ion migration and electrical conduction. OHPs have an ABX 3 crystal structure; the A-site cation is located at the center of a BX 6 octahedral cage, and the B-site metal cation is surrounded by the six nearest-neighbor X-site halide anions. [7] OHPs have a significant hysteresis property that is caused by ion migration or space charges, or both, which may enable gradual modulation of conductance in OHP. [8] Two-terminal artificial synapses based on 3D methylammonium (MA) lead halide perovskite (MAPbX 3 , X = Br, I) films showed synaptic responses that are caused by ion migration in the OHP layer. [9,10] Ion migration in 3D OHP film is induced by relatively low activation energy and a low energy consumption of ≈20 fJ per synaptic event was achieved in the synaptic devices. However, the energy consumption could be further reduced to the energy level of biological synapses when the ion migration was controlled by engineering the structure of OHP films could be optimally done.In this work, we introduce 2D and quasi-2D OHP films into artificial synapses to enable control of ion migration and resultant synaptic responses. For this purpose, we replaced the small MA ion with a bulky phenethylammonium (PEA) ion in their crystalline structures. To prepare 2D, quasi-2D, and 3D OHP films, we controlled the stoichiometric ratio of PEA and MA cations to induce self-assembly of a layered structure. This replacement of an MA cation with PEA cation suppresses ion migration in the out-of-plane direction of the OHP films. [11][12][13] Thereby, the activation energy E A of ion migration is increased, so ion migration and excitatory postsynaptic current (EPSC) can be reduced. Also, energy consumption of the device is reduced to ≈0.7 fJ per synaptic event, which is comparable to that of biological synapses. Memory retention of artificial The hysteretic behavior of organic-inorganic halide perovskites (OHPs) are exploited for application in neuromorphic electronics. Artificial synapses with 2D and quasi-2D perovskite are demonstrated that have a bulky organic cation (phenethylammonium (PEA)) to form structures of (PEA) 2 MA n-1 Pb n Br 3n+1 . The OHP films have morphological properties that depend on their structure dimensionality (i.e., n value), and artificial synapses fabricated from them show synaptic responses such as short-term plasticity, paired-pulse facilitation, and long-term plasticity. The operation mechanism of OHP artificial synapses are also analyzed depending on the dimen...

Tunable Synaptic Plasticity in Crystallized Conjugated Polymer Nanowire Artificial Synapses

“…Here, the duration of the spike varies from 28 to 215 ms, and EPSC increased with increasing duration. An increased number of spikes can mimic repeated rehearsal processes to modulate synaptic plasticity . SNDP was also observed in our artificial synapses (Figure g).…”

“…Lee and coworkers prepared 2D, quasi‐2D, and 3D halide perovskite artificial synapses and studied dimensionality‐dependent plasticity. The retention time of postsynaptic currents can be controlled by adjusting the dimensionality of the perovskite layer . They also demonstrated a synaptic–property–tunable synaptic transistor (ST) using a single intrinsic semiconducting polymer that emulates universal synaptic behaviors of both brain and peripheral nervous systems by simply adjusting the annealing temperature .…”

Graphdiyne-Based Ultra-Responsive Artificial Synapse with Multi-Ion Diffusive Dynamics for Mimicking Efferent Nerves

“…3a). 46 This plasticity can also be observed under the action of negative pulses ( Supplementary Fig. 3a).…”

Achieving Microstructure‐Controlled Synaptic Plasticity and Long‐Term Retention in Ion‐Gel‐Gated Organic Synaptic Transistors

“…[ 32,33 ] The ion trapping could lead to stable current retention in long‐term potentiation, which is important for implementing long‐term memory behavior in neuromorphic computing. [ 11,37 ] In an IGOST with an ODTS annealed film, PSC was retained after 12 min without any noticeable decay; the current retention was clearly different from that of the as‐spun@bare film, in which PSC decays within a few minutes. During the continuous current reading, PSC in the IGOST that used annealed@SAM film started to increase slightly after 10 min; this change may be caused by moisture absorption by the ion gel in ambient air.…”