The light trapping properties of textured optical sheets have become of recent interest in photovoltaic energy conversion since light trapping allows a significant reduction in the thickness of active solar cell material. Previous analyses have concentrated on sheets with randomly textured (Lambertian) surfaces. The texturing of crystalline silicon substrates with anisotropic etches to give surfaces covered by square based pyramids defined by intersecting (111) crystallographic planes is a widely used technique for reflection control in silicon solar cells. This paper analyzes the light trapping properties of substrates with such pyramidally textured surfaces. Important differences are found from the case of Lambertian surfaces with practical consequences for the design of high efficiency silicon solar cells.

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Significant photocurrent enhancement has been achieved for evaporated solid-phase-crystallized polycrystalline silicon thin-film solar cells on glass, due to light trapping provided by Ag nanoparticles located on the rear silicon surface of the cells. This configuration takes advantage of the high scattering cross-section and coupling efficiency of rear-located particles formed directly on the optically dense silicon layer. We report short-circuit current enhancement of 29% due to Ag nanoparticles, increasing to 38% when combined with a detached back surface reflector. Compared to conventional light trapping schemes for these cells, this method achieves 1/3 higher short-circuit current.

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