Performance of silicon heterojunction solar cells with various metal-electrodes directly formed on a-Si films without insertion of TCO

Abstract

For further reduction of the fabrication cost of interdigitated back-contact (IBC) crystalline-silicon (c-Si) heterojunction (SHJ) solar cells, we investigated the performance of SHJ solar cells with directly metallized electrodes on catalytic chemical vapor deposited (Cat-CVD) amorphous Si (a-Si) films without insertion of any transparent conductive oxide (TCO) layers. From the evaluation of the current density–voltage (–V) characteristics of solar cells fabricated with various metal-electrodes such as silver (Ag), aluminum (Al), palladium (Pd), and nickel (Ni), and with post-annealing after forming the metal-electrodes, it is found that Al is most suitable as the metal for electrode, and that if Al is used the post-annealing up to 150 °C is effective for improving the cell performance. From the secondary ion mass spectrometry (SIMS) experiments, it is revealed that Al did not seriously diffuse into Cat-CVD a-Si for the annealing below 150 °C, and that thickness of p-a-Si>20 nm is effective to prevent reduction ofVOC due to Al diffusion. The results demonstrate that Al direct metallization on Cat-CVD a-Si films is applicable for IBC-SHJ solar cells by taking care of postannealing temperature up to 150 °C and the thickness of p-a-Si.