Back-surface-field effects at the heterojunctions between boron-doped p-type hydrogenated amorphous silicon and crystalline silicon in thin-film crystalline silicon solar cells

We have found that the back-surface recombination velocity, S-b, of minority carriers in crystalline silicon (c-Si) thin film solar cells can be reduced to less than 10(3) cm/s when a boron (B)-doped p-type hydrogenated amorphous silicon (a-Si:H) layer is deposited on the back surface of a p-type c-Si substrate at 200 degrees C, while the value of S-b is 10(6) cm/s when a B-doped p-type layer is epitaxially grown on the c-Si substrate. We have clarified, from internal photoemission (IPE) and attenuated-total-reflection Fourier transform infrared (ATR-FTIR) spectroscopy measurements, that the band lineup of the heterojunction between B-doped p-type a-Si:H and c-Si and the hydrogen passivation of defects in B-doped a-Si:H are possible reasons for the observed low value of S-b.