Reversibility and transport properties of dithienylethene photoswitches.

We consider a particular class of molecular electronic devices (MEDs) built around the photoactive dithienylethene switch. Light of an appropriate frequency can convert the switch from a high to a low conductance form. Various derivatives of the dithienylethene that have recently been investigated experimentally are modeled. The transmission probabilities for the switches are analyzed and we provide an explanation for why certain switches, as a part of a MED, can only be converted from the closed to the open form, while for other switches, this process is reversible.