Resonant enhancement of metal nanoparticle arrays fabricated with nanoimprint lithography

Plasmonic effects on metal particles are a promising way of trapping light in solar cells. We experimentally demonstrate enhanced absorptance in thin silicon using metal nanoparticle arrays in conjunction with a rear mirror. The nanoimprint process is a fast and scaleable method for producing nanoscale light trapping structures. Incorporating both nanoparticle arrays and a rear mirror leads to a substantial increase in absorptance, due to resonant interference effects. We numerically simulate a planar Ag mirror deposited onto a planarized sol-gel silicon dioxide (SiO2) layer, and show the enhancement could reach 53%. We also find that a conformal Ag mirror deposited on a sputtered SiO2 layer could give similar enhancement. Experimentally, we derive predicted Jsc enhancements of up to 2.8 mA/cm2 from absorptance measurements. The experimental results show good qualitative agreement with numerical simulations as the thickness is increased, with clear evidence of absorptance enhancement via a Fabry-Perot resonance effect.