Application of a-Si/μc-Si hybrid layer in tunnel oxide passivated contact n-type silicon solar cells

This paper presents our research on the TOP-Con silicon solar cells, which focuses on the passivated contacts based on a thin tunneling oxide layer and a silicon thin film. The influence of the microstructure of silicon thin film on the passivation property was studied. The experimental results indicated that the tunnel oxide combined with a-Si:H featured a good passivation property compared to the μc-Si:H. whereas, the annealed μc-Si:H led to a high fraction of crystallization, and no blistering was observed. A hybrid structure containing a-Si/μc-Si:H thin films was suggested to improve both the passivation and contact properties. The effective carrier lifetime of 3.2 ms and implied Voc of 716 mV were achieved with symmetric structure on n-type Cz substrate, indicating that our tunnel oxide/n+ hybrid-Si provides excellent passivation. The performance of TOP-Con solar cells with hybrid layer at the rear contact has been drastically improved compared to that of cells with μc-Si layer. Although a relatively low efficiency of 15.09% was achieved due to the poor passivation at the front surface, simulations indicated that the conversion efficiency of solar cells can be easily increased to 21.69% (Jsc = 38.93 mA/cm2, Voc = 0.694 V, FF = 80.29%) by improving the front surface passivation and reducing the front surface reflectivity.