Triple-functional n-type microcrystalline silicon oxide layers in hydrogenated amorphous silicon/microcrystalline silicon tandem solar cells

A novel tunnel recombination junction (TRJ) consisted of n type hydrogenated microcrystalline silicon oxide (n-μc-SiO_x:H) layer and p type hydrogenated nanocrystalline silicon oxide (p-nc-SiOx:H) layer was proposed in hydrogenated amorphous silicon/microcrystalline silicon (a-Si:H/μc-Si:H) tandem solar cell. The absence of n-μc-Si:H compared to conventional n-μc-SiO_x:H/n-μc-Si:H/p-nc-SiO_x:H TRJ reduced parasitic absorption. Meanwhile, the new TRJ indicated an ohmic contact, which is suitable for the tandem solar cell. The application of the new TRJ significantly improved the short-circuit current (J_sc) of bottom cell. Moreover, n-μc-SiOx:H layer functioned as intermediate reflector layer to ensure high J_sc of top cell. Initial conversion efficiency of optimized a-Si:H/μc-Si:H tandem solar cell with novel TRJ based on as-grown MOCVDZnO: B (BZO) substrate reached up to 12.99%.