Surface plasmon enhanced photocurrent in thin GaAs solar cells

Abstract

We report fabrication of size-controlled plasmonic nanoparticle arrays by which optically thin GaAs single junction solar cells are decorated. Ordered Ag and Al nanoparticles with average diameters of 60-150 nm and interparticle spacings of 100-300 nm were templated onto the window layers of the GaAs solar cells using nanoporous anodic aluminum oxide membrane templates. Near the surface plasmon resonances, 60nm-diameter Ag and Al nanoparticles serve as light-absorbers so that non-radiative surface plasmon resonances reduce the photocurrent of the cells, which is improved by increasing the nanoparticle size. Photocurrent enhancements are seen at wavelengths longer than surface plasmon resonance which is maximized near the band gap edge of GaAs. These enhancements can be attributed to the increased optical path in the photovoltaic layers resulting from multi-angle scattering by the nanoparticles, while high scattering efficiency nanoparticles in turn increase the back scattering light out of the cell reducing the photocurrent.