Heterostructures, such as the crystalline silicon (c-Si) /plasma-enhanced chemical vapor deposited (PECVD) hydrogenated amorphous silicon (a-Si:H) structure, form a possibility in the development of a low recombination rear contact for photovoltaic devices fabricated from p -type c-Si (p) substrates. To find a good compromise between limited charge carrier recombination at the surface and a limited resistivity of the contact, a sandwich structure, such as c-Si (p) a-Si:H (i) a-Si:H (p+) has been proposed in the past. However, in this letter, we report that whereas a very thin intrinsic a-Si:H layer (∼3 nm) may still yield very low values for the surface recombination velocity of low resistivity (0.5-1.5 Ω cm) c-Si (p) wafers, the surface passivation properties are lost when this intrinsic film is subsequently covered by a PECVD a-Si:H (p+) layer. This phenomenon suggests that surface recombination does not take place at the c-Si (p) a-Si:H (i) interface, but more likely in the defect-rich PECVD a-Si:H (p+) material, by tunneling of minority carriers through the thin a-Si:H (i) layer.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)