Light trapping in monocrystalline Si solar cells using back-side diffraction gratings

摘要

Back-side diffraction gratings enhance a solar cell's near--band--gap response by diffracting light into higher orders and thereby reducing front--side escape losses. The resulting increased photon absorption and carrier generation improves short--circuit current densities and solar cell efficiencies. Combining rigorous coupled--wave analysis and ray tracing yields a three--dimensional, polarization sensitive optical model to calculate Si absorbance, front--side and back--side losses. For industrially used, pyramidally textured, 180μm Si solar cells with 85 nm SiN_x. anti--reflection coating, the application of an optimized back-side grating enhances the short--circuit current density by ≈ +1 mA/cm~2, a relative increase of ≈ +2.7 %.