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Hydrogenation of polycrystalline silicon (poly-Si) passivating contacts is crucial for maximizing their passivation performance. This work presents the application of Al 2 O 3 prepared by atomic layer deposition as a hydrogenating capping layer. Several important questions related to this application of Al 2 O 3 are addressed by comparing results from Al 2 O 3 single layers, SiN x single layers, and Al 2 O 3 /SiN x double layers to different poly-Si types. We investigate the effect of the Al 2 O 3 thickness, the poly-Si thickness, the poly-Si doping type, and the postdeposition annealing treatment on the passivation quality of poly-Si passivating contacts. Especially, the Al 2 O 3 /SiN x stack greatly enhances the passivation quality of both n + and p + doped as well as intrinsic poly-Si layers. The Al 2 O 3 layer thickness is crucial for the single-layer approach, whereas the Al 2 O 3 /SiN x stack is less sensitive to the thickness of the Al 2 O 3 layer. A thicker Al 2 O 3 layer is needed for effectively hydrogenating p + compared to n + poly-Si passivating contact. The capping layers can hydrogenate poly-Si layers with thicknesses up to at least 600 nm. The hydrogenation-enhanced passivation for n + poly-Si is found to be more thermally stable in comparison to p + poly-Si. These results provide guidelines on the use of Al 2 O 3 capping layers for poly-Si contacts to significantly improve their passivation performance. Index Terms-Atomic layer deposition (ALD) Al 2 O 3 , hydrogenation, passivation quality, polycrystalline silicon (poly-Si) passivating contacts, thermal stability. I. INTRODUCTIONC RYSTALLINE silicon (c-Si) solar cells with polycrystalline silicon (poly-Si) as passivating contacts enable Manuscript

Discharge current components, such as electron, ion beam, and lost-to-wall currents, are obtained as functions of azimuthal propellant inhomogeneity in a Hall thruster. Discharge characteristics are discussed based on discharge current oscillation and radial–azimuthal discharge photography. A highly oscillative operation regime is found to be accompanied by radially enlarged expansion of discharge under limited electron currents. Further increases in neutral inhomogeneity lead to quiescent discharge combined with enhanced electron currents and an azimuthally separated ionization region. An axial one-dimensional classical view of electron flow is found to explain the observed electron current evolution only until moderate propellant inhomogeneity occurs. Through discharge image analysis, it is shown that plasma inhomogeneity increases linearly with respect to the input neutral particle inhomogeneity. The evolution of the inhomogeneity does not capture a stepwise increase in the electron current during discharge mode changes; however, the monotonic increase featured in each discharge regime shows that the azimuthal gradient of plasma properties can contribute to increased electron current. Lastly, the weakened magnetic barrier to electron flow resulting from axial–azimuthal variation in plasma structures is presented as another possible cause of increased electron current in nonuniform propellant operations.

In this paper break-through results on our 6" industrial Mercury cells are presented. We gained more than 1% absolute in efficiency by optimizing the processes and design of the cells, resulting in 20.9% cell efficiency. We used standard industrial equipment and the number of process steps similar to our commercial n-Pasha technology. The screen-printed IBC cells can be interconnected by our proven industrial foil-based interconnection scheme. Together with this result, we present a method to characterize and quantify the pn-junction recombination contribution to V oc and pseudo-FF losses in the cell. Finally, our roadmap to 23% Mercury cells is presented.