Nanoparticle-induced enhancement and suppression of photocurrent in a silicon photodiode.

Nanoparticles are capable of both enhancing and suppressing the photocurrent in a silicon diode when deposited on the active face of the device. Photocurrent imaging of the individual nanoparticles and nanoparticle aggregates responsible for this effect reveals that Au nanospheres, nanoshells, and nanoshell dimers each exhibit unique wavelength-dependent suppression-enhancement characteristics. In contrast, silica nanospheres provide a sizable and relatively uniform photocurrent enhancement across the same spectral range (532-980 nm). Unusual light-harvesting behavior observed correlates with a highly complex energy flow (optical "vortexing") for the forward scattered light of plasmon resonant nanoparticles into the device.