Unveiling the Role of Side Chain for Improving Nonvolatile Characteristics of Conjugated Polymers-Based Artificial Synapse

Interest has grown in services that consume a significant amount of energy, such as large language models (LLMs), and research is being conducted worldwide on synaptic devices for neuromorphic hardware. However, various complex processes are problematic for the implementation of synaptic properties. Here, synaptic characteristics are implemented through a novel method, namely side chain control of conjugated polymers. The developed devices exhibit the characteristics of the biological brain, especially spike-timing-dependent plasticity (STDP), high-pass filtering, and long-term potentiation/depression (LTP/D). Moreover, the fabricated synaptic devices show enhanced nonvolatile characteristics, such as long retention time (approximate to 102 s), high ratio of Gmax/Gmin, high linearity, and reliable cyclic endurance (approximate to 103 pulses). This study presents a new pathway for next-generation neuromorphic computing by modulating conjugated polymers with side chain control, thereby achieving high-performance synaptic properties. In organic semiconductors-based neuromorphic devices, it is difficult to endow long-term plasticity in diketopyrrolopyrrole (DPP) polymers due to insufficient interaction with ions. In this article, a rational way is proposed to overcome the deficiency of nonvolatile properties by tailoring the length of the alkyl side-chain of DPP polymers. image