Silicon nanowire arrays passivated by Al2O3/TiO2 stack layers

To reduce reflectance on heterojunction silicon nanowire (SiNW) solar cells with the structure of ITO/p-type hydrogenated amorphous silicon(a-Si:H)/n-type SiNWs embedded in dielectric materials for passivation/n-type a-Si:H/back electrode, stack layers of aluminum oxide (Al₂O₃) and titanium oxide (TiO₂) were deposited on SiNW arrays by atomic layer deposition (ALD). Refractive index of TiO₂ prepared by ALD was 2.5 in a visible spectral range. The effective minority carrier lifetime in SiNW arrays embedded in an Al₂O₃/TiO₂ stack layer of 94 μsec was obtained, which was comparable to an Al₂O₃ single layer. The surface reflectance of SiNW solar cells was drastically decreased below around 5% in all the wavelength range using the Al₂O₃/TiO₂/Al₂O₃ stack layer.