Reduction in connecting resistivity and optical reflection loss at intermediate layer for mechanically stacked multijunction solar cells

Abstract

Reduction in the connecting resistivity and optical reflection loss at the intermediate region of mechanically stacked multijunction solar cells are discussed. The top and bottom substrates were bonded using an epoxy-type adhesive with dispersed transparent and conductive indium tin oxide (ITO) particles. The connecting resistivity of the intermediate layer was substantially decreased to 0.12 Ω cm2 for the stacked Si substrates with 40 nm surfaces roughened by SF6/Ar plasma irradiation. The optical reflectivity of the stacked GaAs and Si substrates was well decreased by the insertion of 130-nm-thick transparent and conductive indium gallium zinc oxide (IGZO) layers at the interfaces between the semiconductor substrates and the intermediate adhesive. The IGZO layers functioned as antireflection layers and provided high effective absorbance to the bottom Si substrates for light wavelength regions, in which the top GaAs substrate was transparent and the bottom Si substrate was opaque. The effective absorbencies at incident light angles between 0 and 50° ranged from 0.94 to 0.95 for the stacked GaAs and Si structure with IGZO layers, and from 0.80 to 0.82 for the structure without IGZO layers.

The Intermediate Connection of Subcells in Si‐based Tandem Solar Cells

“…For the conductive composite layer, a series of conducting agents such as metal grids, [82] metal spheres [81,83] silver nanowires, [84] and ITO particles [85,86] can be dispersed into a transparent polymer film to form an intermediate layer with transparency and conductivity. For instance, a TCA layer consisting of silver-coated poly-(methyl methacrylate) (PMMA) microspheres and transparent epoxy was developed.…”