Side chain engineering enhances the high-temperature resilience and ambient stability of organic synaptic transistors for neuromorphic applications

Organic synaptic transistors are considered to be one of the most promising device concepts for neuromorphic systems. However, repressively low memory retention and high-temperature instability greatly preclude the development and real-world application of organic synaptic transistors. Herein, we reported three conjugated polymers based on a bithiophene-thienothiophene backbone and the traditional ethylene glycol (EG) chains substituted by more hydrophobic propylene glycol (PG) and butylene glycol (BG) counterparts for three-terminal organic neuromorphic memory devices (TONMD). The resulting TONMD exhibits superior viability in ambient and high-temperature environments. BG chain-based p(b2T-TT) show ultra-long memory retention of over 103 s and large analog switching range (>10 ×) at 180 °C, which represents the record-high high-temperature resilience for reported TONMD to date. They also demonstrated excellent endurance of over 105 write-read operations and ultra-high ambient stability with 96 % of its original conductance after 3 months. Data of molecular dynamic simulations and microstructure show that the superior high-temperature resilience and ambient stability originate from more rigid conformation and stable morphology with the increased hydrophobicity of the PG and BG functionalities. Overall, rational design of oligoether side-chains will boost the device's dual high-temperature and ambient stability without compromising synaptic function and provide promising strategies for high-temperature neuromorphic applications.