Significant enhancement of radiative efficiency of thin-film silicon light-emitting diodes achieved by placing the active layer in close proximity to silver (Ag) nanoparticles has been observed. In this paper, optical properties including transmission, reflection, and absorption of a random assembly of Ag nanoparticles are theoretically investigated using the effective medium model. Furthermore, the influence of Ag nanoparticles on light emission of silicon light-emitting diodes is studied by an improved effective mode volume model we propose here. The normalized line shape of dipole oscillation is calculated directly using Lorentz-Drude model without using any approximation. Thus, it results in more accurate calculation of the enhanced Purcell factor in comparison with the conventional approach. We show that an enhancement of radiative efficiency of silicon light-emitting diodes can be achieved by localized surface plasmons on metal nanoparticles. The calculated result of optimal Ag nanoparticle size to enhance light emission of silicon light-emitting diodes at 900 nm wavelength is in very good agreement with those obtained from the experimental result. The model is useful for the design of metallic nanoparticles enhanced light emitters.
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