MOLECULAR SWITCH BASED ON BITHIOPHENE-AZOBENZENE: HOW TO CONTROL CONDUCTANCE THROUGH THE MONOLAYER USING LIGHT
Molecular switches based on azobenzene (azo) are defined as light-responsive molecules which can change between two configurational states under light stimuli. Responsive azo monolayers can be used to modulate the work function, i.e. they tune the properties of the interfaces at the electrodes. In this work, we investigate what happens to the structures, electronic properties, and the charge redistribution within azo-bithiophene (azo-bt) monolayers depending on the light stimulus using density functional theory. Two types of switches differing in the order of azo and bt counting from the anchor group are modelled: azo-bt and bt-azo . One of them (bt-azo) is known from the literature, the remaining one is a product of rational design. We describe trans- and cis-isomers for each switch being in a contact with a gold cluster. Our simulations explain a giant ON/OFF conductance ratio upon UV light stimulus by improved electronic coupling between the cis-isomers (ON-state) and the gold cluster. The trans-isomers (OFF-state) of the simulated switches play the role of the insulators. Moreover, we show which molecular properties are enchanced by molecular design. This study opens up new avenues to the development of the innovative design of electrode surface modifications.