Atomic-layer-deposited aluminum oxide for the surface passivation of high-efficiency silicon solar cells

We present independently confirmed efficiencies above 20% for PERC-type solar cells with the point-contacted rear being either passivated by atomic-layer-deposited Al2O3 or by stacks consisting of an ultrathin Al2O3 film and a thicker PECVD-SiOx layer. Internal quantum efficiency measurements reveal that the effective rear surface recombination velocities of the single-layer Al2O3-passivated cells are comparable to those measured on reference cells passivated by an aluminum-annealed thermal SiO2, while those of the Al2O3/SiOx-passivated cells are even lower. Very low effective rear surface recombination velocities of only 70 cm/s are reported for the Al2O3/SiOx stacks, including metalized areas on the cell rear.