Optimization of Amorphous Si/Crystalline Si Heterojunction Solar Cells by BF2 Ion Implantation

Abstract

In this study we evaluated two approaches to improving the efficiency of amorphous Si/crystalline Si (a-Si/c-Si) heterojunction solar cells by BF2 ion implantation. First, emitter layer formation was compared for the cases of B and BF2 ion implantation when using the same 7° tilt angle. Second, emitter layer formation was compared between a 7° tilt angle and a 60° tilt angle when using BF2 ion implantation. The experimental results reveal that the fluorine in BF2 passivates the defects at the a-Si and a-Si/c-Si interface, and ion implantation at a high 60° tilt angle forms a shallow solar cell junction. The emitter layer formed by BF2 ion implantation with a 60° tilt angle in an a-Si/c-Si heterojunction solar cell achieves the highest short circuit current density (JSC) of 36.85 mA/cm2 with a conversion efficiency (η) of 14.41%.