Molecular rectification, photodiodes and symmetry

We present a review of recent advances in the molecular rectifier project. Using a donor - -bridge - acceptor compound, specifically designed to be a molecular rectifier, drastically improved rectifier characteristics were observed compared with a previously published -bridged compound. In particular the increased `rectification ratio' of the -bridged compound was attributed to more effective current blocking under reverse bias. Furthermore, we demonstrate that photodiode-like properties are possessed by films of the zwitterionic, -bridged compound, - , using a transparent electrode construction. Finally, we provide an explanation for the observation that all non-centrosymmetric Langmuir - Blodgett film samples exhibit an exponential current-density/voltage dependence.