Surface-Plasmon Enhanced Near-Bandgap Light Absorption in Silicon Photovoltaics

An extended Mie scattering theory is used in this paper to analyze the surface-plasmon enhanced light absorption in silicon for photovoltaic applications. The calculation results show that the optical absorption in silicon can be enhanced up to 50 times at resonance frequency by embedded spherical silver nanoparticles due to the local field enhancement by surface plasmons. The analysis reveals that the surface-plasmon field is concentrated in a spherical shell that encloses the particle. The enhancement reaches maximum when the thickness of the shell is 0.26 times the radius of the particle. The maximum absorption enhancement is found to be induced by silver particles with intermediate radii. The enhancement with larger particles is limited by the retardation effect, while the smaller-particle assisted absorption is hampered by electron scattering on the particle surface.