Intermediate amorphous silicon layer for crystalline silicon passivation with alumina

Abstract

The passivation of silicon surfaces is required to reach high-efficiency with most of modern solar cell device structures. It has been demonstrated that the deposition of charged dielectric layers such a-SiNx:H or Al2O3 on the silicon surface is an efficient passivation technology. In particular, the Al2O3 material is efficient to passivate p-type silicon surfaces, providing lifetimes greater than 1 ms for those with layers deposited by the ALD technique. Other deposition techniques, like magnetron sputtering, have not succeeded to provide this level of passivation, probably due to the damage caused on the silicon wafer surface by the high-energy deposition process. As a solution, we assume that an intrinsic a-Si:H very thin interlayer can serve both as a physical protection layer and as a source of hydrogen atoms for surface chemical passivation. In this regard, we have developed a new approach based on the use of an intrinsic a-Si:H interlayer between the silicon wafer and the 50-nm thick passivation layer of amorphous Al2O3 deposited by sputtering. The results, obtained by QSSPC measurements, demonstrated effective lifetimes in the range of 1-2 ms for both n-type and p-type float zone silicon wafers covered with the a-Si:H/Al2O3 passivation layers and after an annealing process at 350 °C.Peer ReviewedPostprint (published version