Impact of ageing on AlOx layer passivation properties for advanced cell architectures

Aluminum oxide (AlOx) is of great interest for the application of crystalline silicon (c-Si) solar cells. Such films combine a chemical passivation, leading to a drastic decrease of the interfacial defect density, with a field effect passivation, thanks to its negative fixed charge which shields the minority carriers from the semiconductor interface. However, despite the interesting passivation properties of AlOx, this work focuses on the passivation stability over time. The correlated influence of the AlOx thickness and of the precleaning, on the AlOx passivation properties, and its stability over time with respect to thermal budget have been clearly demonstrated. The deposition of a SiNx capping layer has been proposed to decrease the kinetic of the degradation. Finally, iPERC AlOx based cells have been processed leading to η=17,2% with advanced front metal deposition (Cu plating).