This paper investigates the use of localized surface plasmons on silver nanoparticles to enhance the absorbance of silicon solar cells. The study shows that surface plasmons can significantly increase the spectral response of thin-film cells over almost the entire solar spectrum. At wavelengths close to the band gap of silicon, there is a significant enhancement of absorption for both thin-film and wafer-based structures. The results show a sevenfold enhancement for wafer-based cells at 1200 nm and up to 16-fold enhancement at 1050 nm for 1.25 μm thin silicon-on-insulator (SOI) cells. The results are compared with a theoretical dipole-waveguide model. The study also reports a close to 12-fold enhancement in the electroluminescence from ultrathin SOI light-emitting diodes and investigates the effect of varying the particle size on that enhancement. Silicon is the material of choice for photovoltaic applications due to its low cost, abundance, nontoxicity, long-term stability, and well-established technology. However, the cost of photovoltaic modules still needs to be significantly reduced for large-scale implementation. One proposed approach is the use of very thin silicon absorbers in thin-film or second-generation photovoltaic cells. Thin-film silicon solar cells have a Si absorber thickness on the order of a few micrometers and are deposited on foreign substrates. However, the efficiencies of such silicon thin-film cells are lower compared to wafer-based silicon cells due to poor light absorption and high bulk and surface recombination. Because thin-film solar cells are only a few microns thick, standard methods of increasing light absorption cannot be used. Plasma etch techniques can damage the silicon, reducing cell efficiency. Another alternative is the texturing of the substrate, but this increases recombination losses. The study demonstrates that surface plasmons on silver nanoparticles can enhance the absorption and emission of silicon solar cells without increasing recombination losses. The study shows that the surface area of silicon and surface passivation layer remain the same as for a planar cell, so surface recombination losses are not expected to increase. The electromagnetic properties of metal particles have been known for a long time, but there has been renewed interest in recent years due to new nanofabrication techniques. Localized surface plasmons (SP) are collective oscillations of the conduction electrons in metal particles. The extinction of the particles is defined as the sum of the scattering and absorption. The scattering and absorption depend on the size of the particles. Metallic particles that are much smaller than the wavelength of light tend to absorb more and hence extinction is dominated by absorption in the metal particles. Absorption dissipates heat and is utilized in applications like solar glazing, nanoscale lithography, and therapeutic applications. However, as the size of the particles increases, extinction is dominated by scattering. The resonance frequencyThis paper investigates the use of localized surface plasmons on silver nanoparticles to enhance the absorbance of silicon solar cells. The study shows that surface plasmons can significantly increase the spectral response of thin-film cells over almost the entire solar spectrum. At wavelengths close to the band gap of silicon, there is a significant enhancement of absorption for both thin-film and wafer-based structures. The results show a sevenfold enhancement for wafer-based cells at 1200 nm and up to 16-fold enhancement at 1050 nm for 1.25 μm thin silicon-on-insulator (SOI) cells. The results are compared with a theoretical dipole-waveguide model. The study also reports a close to 12-fold enhancement in the electroluminescence from ultrathin SOI light-emitting diodes and investigates the effect of varying the particle size on that enhancement. Silicon is the material of choice for photovoltaic applications due to its low cost, abundance, nontoxicity, long-term stability, and well-established technology. However, the cost of photovoltaic modules still needs to be significantly reduced for large-scale implementation. One proposed approach is the use of very thin silicon absorbers in thin-film or second-generation photovoltaic cells. Thin-film silicon solar cells have a Si absorber thickness on the order of a few micrometers and are deposited on foreign substrates. However, the efficiencies of such silicon thin-film cells are lower compared to wafer-based silicon cells due to poor light absorption and high bulk and surface recombination. Because thin-film solar cells are only a few microns thick, standard methods of increasing light absorption cannot be used. Plasma etch techniques can damage the silicon, reducing cell efficiency. Another alternative is the texturing of the substrate, but this increases recombination losses. The study demonstrates that surface plasmons on silver nanoparticles can enhance the absorption and emission of silicon solar cells without increasing recombination losses. The study shows that the surface area of silicon and surface passivation layer remain the same as for a planar cell, so surface recombination losses are not expected to increase. The electromagnetic properties of metal particles have been known for a long time, but there has been renewed interest in recent years due to new nanofabrication techniques. Localized surface plasmons (SP) are collective oscillations of the conduction electrons in metal particles. The extinction of the particles is defined as the sum of the scattering and absorption. The scattering and absorption depend on the size of the particles. Metallic particles that are much smaller than the wavelength of light tend to absorb more and hence extinction is dominated by absorption in the metal particles. Absorption dissipates heat and is utilized in applications like solar glazing, nanoscale lithography, and therapeutic applications. However, as the size of the particles increases, extinction is dominated by scattering. The resonance frequency