CPC H01L 31/1844 (2013.01) [H01L 31/0543 (2014.12); H01L 31/0547 (2014.12); H01L 31/0687 (2013.01); H01L 31/0725 (2013.01); H01L 31/0735 (2013.01); H01L 31/1892 (2013.01)] | 20 Claims |
1. A solar cell comprising:
an epitaxial sequence of layers of semiconductor material forming at least a top or light facing solar subcell and a second solar subcell having a top surface and a bottom surface and being disposed below the top or light facing solar subcell;
a semiconductor contact layer having a top surface and a bottom surface, the top surface of the semiconductor contact layer being disposed below the bottom surface of the second solar subcell;
a diffusion barrier layer below the bottom surface of the semiconductor contact layer, wherein the diffusion barrier layer has a thickness of between 0.1 nm and 10 nm, and wherein the diffusion barrier layer is composed of Pd or a Pd alloy;
a reflective metal layer having a thickness between 50 nm and 5 microns and being disposed below a bottom surface of the diffusion barrier layer, wherein reflectivity of the reflective metal layer is greater than 80% in the wavelength range 850-2000 nm for reflecting light back toward the second solar subcell; and
a contact metal layer composed of one or more layers of Ag, Au, and Ti disposed on a bottom of said reflective metal layer.
|