  In this paper, we present a theoretical study on the absorption efficiency
enhancement of a thin film amorphous Silicon (a-Si) photovoltaic cell over a
broad spectrum of wavelengths using multiple nanoparticle arrays. The light
absorption efficiency is enhanced in the lower wavelengths by a nanoparticle
array on the surface and in the higher wavelengths by another nanoparticle
array embedded in the active region. The efficiency at intermediate wavelengths
is enhanced by the simultaneous resonance from both nanoparticle layers. We
optimize this design by tuning the radius of particles in both arrays, the
period of the array and the distance between the two arrays. The optimization
results in a total quantum efficiency of 62.35% for a 300nm thick a-Si
substrate.
