A compound-semiconductor photovoltaic cell includes a first photoelectric conversion cell made of a first compound-semiconductor material which lattice matches with GaAs or Ge; a first tunnel junction layer arranged on a deep side farther than the first photoelectric conversion cell in a light incident direction, and including a first p-type (Al.sub.x1Ga.sub.1-x1).sub.y1In.sub.1-y1As (0≤x1<1, 0<y1≤1) layer and a first n-type (Al.sub.x2Ga.sub.1-x2).sub.y2In.sub.1-y2P (0≤x2<1, 0<y2<1) layer; and a second photoelectric conversion cell arranged on a deep side farther than the first tunnel junction layer in the light incident direction, and made of a second compound-semiconductor material which is a GaAs-based semiconductor material. The first photoelectric conversion cell and the second photoelectric conversion cell are joined via the first tunnel junction layer, and a lattice constant of the first n-type (Al.sub.x2Ga.sub.1-x2).sub.y2In.sub.1-y2P layer is greater than a lattice constant of the first photoelectric conversion cell.

A compound-semiconductor photovoltaic cell includes a first photoelectric conversion cell made of a first compound-semiconductor material which lattice matches with GaAs or Ge; a first tunnel junction layer arranged on a deep side farther than the first photoelectric conversion cell in a light incident direction, and including a first p-type (Al.sub.x1Ga.sub.1-x1).sub.y1In.sub.1-y1As (0≤x1<1, 0<y1≤1) layer and a first n-type (Al.sub.x2Ga.sub.1-x2).sub.y2In.sub.1-y2P (0≤x2<1, 0<y2<1) layer; and a second photoelectric conversion cell arranged on a deep side farther than the first tunnel junction layer in the light incident direction, and made of a second compound-semiconductor material which is a GaAs-based semiconductor material. The first photoelectric conversion cell and the second photoelectric conversion cell are joined via the first tunnel junction layer, and a lattice constant of the first n-type (Al.sub.x2Ga.sub.1-x2).sub.y2In.sub.1-y2P layer is greater than a lattice constant of the first photoelectric conversion cell.

Tunnel junctions for multijunction solar cells are provided. According to an aspect of the invention, a tunnel junction includes a first layer including p-type AlGaAs, a second layer including n-type GaAs, wherein the second layer is a quantum well, and a third layer including n-type AlGaAs or n-type lattice matched AlGaInP. The quantum well can be GaAs or AlxGaAs with x being more than about 40%, and lattice matched GaInAsNSb in the Eg range of from about 0.8 to about 1.4 eV.

Tunnel junctions for multijunction solar cells are provided. According to an aspect of the invention, a tunnel junction includes a first layer including p-type AlGaAs, a second layer including n-type GaAs, wherein the second layer is a quantum well, and a third layer including n-type AlGaAs or n-type lattice matched AlGaInP. The quantum well can be GaAs or AlxGaAs with x being more than about 40%, and lattice matched GaInAsNSb in the Eg range of from about 0.8 to about 1.4 eV.

A solar cell includes: an n-type first amorphous silicon layer provided on a first main surface of a crystalline silicon substrate; an amorphous silicon oxide layer provided on a first main surface of the first amorphous silicon layer; and an n-type fine crystal silicon layer provided on a first main surface of the amorphous silicon oxide layer. An oxygen atom concentration in the first amorphous silicon layer, the amorphous silicon oxide layer, and the fine crystal silicon layer has a maximum value in the amorphous silicon oxide layer with a thickness direction.

A multijunction solar cell including interconnected first and second discrete semiconductor regions disposed adjacent and parallel to each other including first top solar subcell, second (and possibly third) lattice matched middle solar subcells; a graded interlayer adjacent to the last middle solar subcell; and a bottom solar subcell adjacent to said graded interlayer being lattice mismatched with respect to the last middle solar subcell; wherein an opening is provided from the bottom side of the semiconductor body to one or more of the solar subcells so as to allow a discrete electrical connector to be made extending in free space and to electrically connect contact pads on one or more of the solar subcells.

A multijunction solar cell including interconnected first and second discrete semiconductor regions disposed adjacent and parallel to each other including first top solar subcell, second (and possibly third) lattice matched middle solar subcells; a graded interlayer adjacent to the last middle solar subcell; and a bottom solar subcell adjacent to said graded interlayer being lattice mismatched with respect to the last middle solar subcell; wherein an opening is provided from the bottom side of the semiconductor body to one or more of the solar subcells so as to allow a discrete electrical connector to be made extending in free space and to electrically connect contact pads on one or more of the solar subcells.

Discussed is a tandem solar cell manufacturing method including etching a crystalline silicon substrate, whereby a solar cell can be obtained which does not have a pyramid-shaped defect on a surface of the substrate, inhibits the generation of a shunt through the substrate having excellent surface roughness properties, and can secure fill factor properties, the solar cell being capable of being obtained through the tandem solar cell manufacturing method. The method includes preparing a crystalline silicon substrate; performing an isotropic etching process of the substrate; and removing a saw damage on a surface of the substrate by performing an anisotropic etching process of the isotropically etched substrate.

Discussed is a tandem solar cell manufacturing method including etching a crystalline silicon substrate, whereby a solar cell can be obtained which does not have a pyramid-shaped defect on a surface of the substrate, inhibits the generation of a shunt through the substrate having excellent surface roughness properties, and can secure fill factor properties, the solar cell being capable of being obtained through the tandem solar cell manufacturing method. The method includes preparing a crystalline silicon substrate; performing an isotropic etching process of the substrate; and removing a saw damage on a surface of the substrate by performing an anisotropic etching process of the isotropically etched substrate.

Presented herein are embodiments of a tandem solar panel subunit with 2-terminals, made from two 3-terminal cell tandems, whose top-cells are strongly current-mismatched to the Si 3-terminal bottom cell.