Al2O3/TiO2 nano-pattern antireflection coating with ultralow surface recombination

We present a nano-patterned dielectric coating for crystalline Si solar cells that combines excellent anti-reflection and passivation properties. The nano-patterned coating comprises an array of TiO₂ nanocylinders placed on top of an ultra-thin Al₂O₃ layer on a flat Si(100) wafer. The antireflection effect stems from the preferential forward scattering of light through leaky Mie resonances in the TiO₂ nanocylinders. The Al₂O₃ layer provides excellent passivation of the Si surface. We experimentally demonstrate ultralow surface recombination with carrier lifetimes above 4 ms, combined with a reflectivity of 2.8% averaged over a broad spectral range.