  It was recently suggested that molecular junctions would be excellent
elements for efficient and high-power thermoelectric energy conversion devices.
However, experimental measurements of thermoelectric conversion in molecular
junctions have indicated rather poor efficiency, raising the question of
whether it is indeed possible to design a setup for molecular junctions that
will exhibit enhanced thermoelectric performance. Here we suggest that hybrid
single-molecule nanoparticle junctions can serve as efficient thermoelectric
converters. The introduction of a semiconducting nanoparticle introduces new
tuning capabilities, which are absent in conventional metal-molecule-metal
junctions. Using a generic model for the molecule and nanoparticle with
realistic parameters, we demonstrate that the thermopower can be of the order
of hundreds of microvolts per degree Kelvin, and that the thermoelectric figure
of merit can reach values close to one, an improvement of four orders of
magnitude improvement over existing measurements. This favorable performance
persists over a wide range of experimentally relevant parameters, and is robust
against disorder (in the form of surface-attached molecules) and against
electron decoherence at the nanoparticle molecule interface.
