Yuan Li1
Tsinghua University1
Molecular switches, which the electrical signal of conductance or voltage can be manipulated by external stimuli, have drawn great attentions recently, with photoswitches the most widely studied due to their theoretically ultrafast switching speed. While light provides a natural, addressable and tunable driving force, molecular photoswitches still suffer poor performance with low on/off ratio of electric current, poor reproducibility, or stochastic switching. One of the reasons is that all the photoswitches with on/off ratio more than 100 are based on the mechanism of molecular photoisomerization, which of the energy barrier is high and not able to provide reproducible fast switch theoretically. In this presentation, I will introduce our recent achievement of a fully reversible photoswitching in large-area self-assembled monolayers by aggregation-induced emission from bending flexible supporting electrodes to crowd the functional tetraphenylethylene molecules generating stable (>1000 reversible on/off cycles) switching with large (3.8 ± 0.1 × 10<sup>3</sup>) on/off ratios with fast (140 ± 10 ms) switching time. The output electrical signal can be controlled by the wavelength of light, or the curvature of electrodes, or a combination of the two stimuli together. Structural characterization supported by spectroscopy and modelling shows mechanically controlled photoswitching relying on aggregation-induced emission with UV light enhancing the Coulomb interaction between the electrons and holes to decrease the energy gap between ground and excited states increasing the conductance through the junctions. Our work shows the possibility of precisely controlling the function of aggregation-induced emission to realize high-performance electronics with molecular level control via simple external mechanical force, which may also be interested by other fields where multi stimuli-responses (light/electric/mechanic) applied/required at micro/nano-region.