18.5% efficient AlO _x /SiN _y rear passivated industrial multicrystalline silicon solar cells

Due to the trend toward thinner and higher efficient crystalline silicon solar cells, excellent rear surface passivation and internal optical reflectance have become more and more important. Aluminum oxide (AlO _x ) capped with silicon nitride (SiN _y ), which is considered as one of the most promising candidates to achieve superior rear passivation and internal reflectance, has to date been mostly used for the rear side of p-type monocrystalline silicon (mono-Si) solar cells. In this paper, we have optimized rear AlO _x /SiN _y stacks deposited by industrial plasma enhanced chemical vapor deposition (PECVD) for multicrystalline silicon (mc-Si) passivated emitter and rear cells (PERC). Sufficient passivation activation effect from industrial fast-firing process and SiN _y deposition process have been demonstrated, so the samples were not subjected to additional thermal treatment process in the cell fabrication flow. For rear AlO _x /SiN _y stack, it is shown that when PECVD AlO _x is thicker than 40 nm, apparent blisters in fired AlO _x deteriorate the cell performance, and the appropriate SiN _y capping is N-rich SiN _y with thickness of at least 180 nm. After process optimization with the least additional process steps, independently confirmed efficiency of 18.5% for Pluto-PERC with PECVD AlO _x /SiN _y rear passivation on standard 156 mm × 156 mm p-type mc-Si wafers has been achieved.