Electromagnetic coupling of light into a silicon solar cell by nanodisk plasmons

Photocurrents of silicon pn junctions patterned with arrays of elliptical Au nanodisks were experimentally and theoretically investigated near the particle plasmon resonance wavelengths, for varying light polarizations and angles of incidence. At plasmon resonance wavelengths, overall backscattering and dissipation were strongly enhanced compared to an unpatterned junction, resulting in lower photocurrents. In contrast, enhanced photocurrents were observed for wavelengths slightly off resonance. Measurements and finite element calculations show that the photocurrent changes occur via plasmon-induced far field effects, rather than by near field enhancement close to the particles. The far field effects are strongly dependent on the particle proximity and coupling to the Si substrate. (C) 2008 American Institute of Physics.