Optimization of Passivation Layer on the Front Surface of N-Type Topcon Solar Cells

In this paper, an effective P-type emitter passivation scheme was proposed by continuously optimizing the passivation layer on the front surface of N-type TOPCon solar cells, that was, adding SiOx layer, using SiOx/AlOx/SiNx tri-layer passivation stacks. The SiOx/AlOx/SiNx stacks combined the benefits of chemical passivation of SiOx and field-effect passivation of AlOx, resulting in high-quality boron-doped emitter passivation. Three different passivation scheme of SiNx, AlOx/SiNx and SiOx/AlOx/SiNx were prepared on the front of N-type TOPCon solar cells. It was revealed that the SiOx/AlOx/SiNx stacks had superior conversion efficiency and the thickness of SiOx had a significant influence on the surface passivation. Through series of optimization of SiOx thickness in the SiOx/AlOx/SiNx stacks, the optimal deposition period of SiOx were determined to be 4 cycles in the PEALD1 process. The N-type TOPCon Solar cells with SiOx/AlOx/SiNx stacks on the front surface exhibited the optimized performances with a conversion efficiency of 24.88% when the deposition period of SiOx was 4 cycles. The efficiency was increased by 0.11%abs., compared with that of the baseline process.