Low-temperature contacts through SixNy-antireflection coatings for inverted a-Si:H/c-Si hetero-contact solar cells
High-temperature contact firing of screen printable metal pastes is getting more problematic as silicon wafers used in solar cell production are becoming thinner. Besides, an electronic degradation of the SixNy/c-Si interface occurs at these temperatures especially if the SixNy layer is directly deposited onto high-quality absorbers as on the front side of a-Si:H/c-Si hetero-contact solar cells of inverted geometry. The latter structure has been proposed as an easy producible high-efficiency solar cell. Low-temperature alternatives such as local ablation of SixNy with 355 nm laser radiation are examined with regard to the stability of the electronic quality of passivated areas between the openings in the SixNy layer. Contactless tinge-resolved microwave conductivity measurements (TRMC) are applied to measure changes in electronic passivation after these treatments. Subsequent galvanic metallization of the openings is optimized for its use as ohmic contacts.