Wet-chemical pre-treatment of c-Si substrates enhancing the performance of a-Sic:H/c-Si heterojunction solar cells
Abstract
The properties of mono-crystalline silicon (c-Si) surfaces after different wet-chemical oxidation and etching steps are investigated regarding the microscopic roughness and electronic properties. For characterization spectral ellipsometry (SE) in the ultraviolet and visible spectral range and photoluminescence measurements (PL) were used. In addition the effect on the performance of a-SixC1-x:H(n)/c-Si(p) heterojunction solar cells were analyzed. A cleaning sequence consisting of an oxidation in hot deionized water and a subsequent etch-back of the thin oxide in ammonium fluoride (NH4F) was found to provide a smooth Si(111) surface with a low defect density compared to standard cleaning sequences. Incorporation of the cleaning sequence in the processing of amorphouscrystalline heterojunction solar cells on textured substrates leads to an increase in the open-circuit voltage as well as the pseudo fill factor.
