Coatings of conducting gold-black nano-structures on commercial thin-film amorphous-silicon solar cells enhance the
short-circuit current by 20% over a broad spectrum from 400 to 800 nm wavelength. The efficiency, i.e. the ratio of the
maximum electrical output power to the incident solar power, is found to increase 7% for initial un-optimized coatings.
Metal blacks are produced cheaply and quickly in a low-vacuum process requiring no lithographic patterning. The
inherently broad particle-size distribution is responsible for the broad spectrum enhancement in comparison to what has
been reported for mono-disperse lithographically deposited or self-assembled metal nano-particles. Photoemission
electron microscopy reveals the spatial-spectral distribution of hot-spots for plasmon resonances, where scattering of
normally-incident solar flux into the plane increases the effective optical path in the thin film to enhance light harvesting.
Efficiency enhancement is correlated with percent coverage and particle size distribution, which are determined from
histogram and wavelet analysis of scanning electron microscopy images. Electrodynamic simulations reveal how the
gold-black particles scatter the radiation and locally enhance the field strength.