Mechanically Controlled High-Performance Molecular Photoswitch

Abstract

Simplified and energy-efficient electronic devices that respond to multiple external stimuli (e.g., voltage, light, and mechanical stress) are needed for nascent technologies ranging from soft robotics and neuromorphic computing to Internet-of-Things1-3. Yet most research to-date focused on one switching modality with one stimulus4-6. Here we align materials design with device technology by introducing mechanical control over photoswitching leading to a new type of dual-gated molecular switch. While molecular switches are inherently energy-efficient7, theoretically ultrafast molecular photoswitches showed disappointing performance to-date, with small on/off ratio of electric current, poor reproducibility, and slow or stochastic switching8,9. It has been particularly challenging to develop efficient photoswitches in molecular tunnel junctions due to quenching and spontaneous back-switching10. On the other hand, molecular mechanical switches have been seldom reported11, despite wide implementation of mechanically-controlled switches12-14. Here, we use mechanical bending of the supporting electrode to direct molecular self-assembly of aggregation-induced emission (AIE) active molecules15,16, which allows us modulate the current under both light and mechanical force. This results in rapid, strong, reliable and sustained molecular switching. The high-performance photoswitch is 10-100 times faster than other approaches with on/off ratio of (3.8±0.1)×103 during 1600 bright/dark cycles under mechanical force, providing an alternative design route for flexible electronics and optomechatronics.