Theoretical Comparison of a Longitudinal versus a Transverse Transport Path through Diarylethene Molecular Switches

Abstract

Diarylethene molecules are regularly used in molecular junctions as light-activated switches. Two crucial parameters drive the performance of these switches: (i) ON–OFF ratios and (ii) reversibility. In this work, we first show using the theoretical NEGF–DFT method that an efficient decoupling between the molecular backbone and the electrodes, which is necessary for reversibility, unfortunately, tends to weaken the ON–OFF ratio. We then show that this trade-off situation can be avoided by considering an alternative “transverse” contact configuration of the diarylethene, which exploits the bond breaking associated with the isomerization reaction. Interestingly, this transverse contact ensures both high on–off ratios (at least by 2 orders of magnitude) and an efficient decoupling of the active unit from the gold electrodes