Low temperature back-surface-field (BSF) technology for crystalline silicon (c-Si) thin film solar cells based on heterojunctions between boron-doped p-type hydrogenated amorphous silicon and c-Si

We propose a low temperature back-surface field (BSF) technology for crystalline silicon (c-Si) thin film solar cells. The BSF structure has a heterojunction between a p-type c-Si substrate and a boron (B)-doped p-type hydrogenated amorphous silicon (a-Si:H) layer deposited on the back surface of the c-Si substrate at 200 degrees C. The back-surface recombination velocity, S-b, Of minority carriers can be reduced to less thap 1000 cm/s in this structure, while the value Of Sb is 10(6) cm/s when a B-doped p-type layer is epitaxially grown on the c-Si substrate. We have clarified, frorn internal hotoemission (IPE) and aftenuated-total-reflection ourier transform infrared (ATR-FTIR) spectroscopy measurements, that possible reasons for the observed low value of S-b are (1) the band lineup of the heterojunction (HJ) between B-doped p-type a-Si:H and c-Si and (2) the hydrogen passivation of defects in B-doped a-Si:H.