Exploiting plasmon-induced hot electrons in molecular electronic devices.

Plasmonic nanostructures can induce a number of interesting responses in devices. Here we show that hot electrons can be extracted from plasmonic particles and directed into a molecular electronic device, which represents a new mechanism of transfer from light to electronic transport. To isolate this phenomenon from alternative and sometimes simultaneous mechanisms of plasmon-exciton interactions, we designed a family of hybrid nanostructure devices consisting of Au nanoparticles and optoelectronically functional porphyin molecules that enable precise control of electronic and optical properties. Temperature- and wavelength-dependent transport measurements are analyzed in the context of optical absorption spectra of the molecules, the Au particle arrays, and the devices. Enhanced photocurrent associated with exciton generation in the molecule is distinguished from enhancements due to plasmon interactions. Mechanisms of plasmon-induced current are examined, and it is found that hot electron generation can be distinguished from other possibilities.

Electronic transport in porphyrin supermolecule-gold nanoparticle assemblies.

Temperature-dependent transport of hybrid structures consisting of gold nanoparticle arrays functionalized by conjugated organic molecules [(4'-thiophenyl)ethynyl-terminated meso-to-meso ethyne-bridged (porphinato)zinc(II) complexes] that possess exceptional optical and electronic properties was characterized. Differential conductance analysis distinguished the functional forms of the temperature and voltage dependences for a range of sample particles and molecular attachments. Thermally assisted tunneling describes transport for all cases and the associated mechanistic parameters can be used to determine the relative roles of activation energy, work function, and so forth. These results provide the basis on which to examine plasmon-influenced conduction in hybrid systems.