Ultraflexible and Energy-Efficient Artificial Synapses Based on Molecular/Atomic Layer Deposited Organic–Inorganic Hybrid Thin Films

Abstract

Flexible artificial synapses, a conjunctive product of brain-inspired neuromorphic computing and wearable electronics, arouse enormous interest in highly connected and energy-efficient neural networks. The organic–inorganic hybrid materials hold great potential in flexible devices due to versatile properties. Here, an organic–inorganic hybrid synaptic device consisting of 2 nm Al2O3 and 22 nm Al-based hydroquinone (Al-HQ) sandwiched between Pt and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrodes is prepared on highly flexible cellophane by molecular/atomic layer deposition (MLD/ALD). The vertically integrated Pt/Al2O3/Al-HQ/PEDOT:PSS device exhibits reliable resistive switching with an ON/OFF ratio greater than 103. Several important bio-synaptic functions, such as long-term potentiation, long-term depression, paired-pulse facilitation, and spike-time-dependent plasticity, are realized in this device with the extremely low energy consumption of ≈25.2 fJ per reset operation, which is ascribed to the unique electron trapping/detrapping and tunneling mechanism. Remarkably, the excellent flexibility and robustness of this hybrid synaptic device is confirmed under the minimum curvature radius of ≈0.7 mm after 104 bending cycles. A pattern recognition computation based on these hybrid synapse devices shows a 90.2% learning accuracy. This research paves a way for the MLD/ALD-derived organic–inorganic-hybrid-based artificial synapse applications in flexible energy-efficient neuron network systems toward system-on-plastics.