MULTIJUNCTION SOLAR CELLS FORMED ON N-DOPED SUBSTRATES
An “n-on-p” type multijunction solar cell structure is disclosed using an n-type substrate for the epitaxial growth of III-V semiconductor material, wherein a “p-on-n” tunnel junction diode is disposed between the substrate and one or more heteroepitaxial layers of III-V semiconductor materials.
1 . A device comprising:
a substrate of n-doped semiconductor material in electrical contact with a metal conductor;
a p-on-n tunnel junction diode disposed above the substrate;
one or more n-on-p junctions disposed above the tunnel junction diode;
a metal grid in electrical contact with the uppermost layer of semiconductor;
together forming a photovoltaic device.
2 . The device according to claim 1 wherein the uppermost layer of semiconductor, in contact with the metal grid, is n-type.
3 . The device according to claim 1 wherein said tunnel junction diode uses p++GaAs on n++GaAs.
4 . The device according to claim 1 wherein the formed photovoltaic device is a triple junction solar cell.
5 . The device according to claim 4 wherein at least one of the n-on-p junctions has a bandgap of approximately 1 eV, or between 0.93 eV and 1.05 eV.
6 . The device according to claim 5 wherein at least a first junction is comprised of a dilute nitride material lattice matched to the substrate.
7 . The device according to claim 6 wherein at least a second junction and a third junction are comprised of Gallium-Arsenide and Indium-Gallium-Phosphide and all the n-on-p junctions are lattice matched to the substrate.
8 . The device according to claim 7 wherein the substrate is comprised of n-type Gallium-Arsenide.
9 . The device according to claim 5 wherein said approximately 1 eV junction is comprised of a material which is not lattice matched to the substrate.
10 . The device according to claim 4 wherein at least one junction is comprised of a Silicon-Germanium material lattice matched to the substrate.
11 . The device according to claim 1 wherein the formed photovoltaic device is a four junction solar cell.
12 . The device according to claim 11 wherein at least a first junction is comprised of a dilute nitride material lattice matched to the substrate.
13 . The device according to claim 1 wherein the formed photovoltaic device is a five junction solar cell.
14 . The device according to claim 13 wherein at least a first junction is comprised of a dilute nitride material lattice matched to the substrate.
15 . The device according to claim 1 wherein said one or more n-on-p junctions include materials identified in Groups III and V of the Periodic Table.