Surface Passivation of Highly and Lowly Doped P-Type Silicon Surfaces with PECVD Al2O3 for Industrially Applicable Solar Cell Concepts

Several aspects of the suitability of PECVD Al2O3 deposition process for solar cell mass production are reported. Among them the throughput, the firing stability, the homogeneity and the repeatability of the process quality have been investigated. Additionally a carrier lifetime higher than 1 ms has been obtained after firing for a layer of only 10 nm combined with a SiNx capping layer. The latter allows an interesting compromise between a low consumption of expensive precursors and a high passivation quality. PECVD Al2O3 has also been studied, in order to offer an industrially suitable solution for the passivation of boron-doped emitters of n-type solar cells. An emitter saturation current density as low as 36 fA cm-2 has been obtained on a 90 Omega/sq emitter with a surface concentration of 7 1019 cm-3, which correspondents to a surface recombination velocity of only 350 cm s-1.