A scalable voltage source having a number N of partial voltage sources implemented as semiconductor diodes connected to one another in series, wherein each of the partial voltage sources has a semiconductor diode with a p-n junction. A tunnel diode is formed between sequential pairs of partial voltage sources, wherein the tunnel diode has multiple semiconductor layers with a larger band gap than the band gap of the p/n absorption layers and the semiconductor layers with the larger band gap are each made of a material with modified stoichiometry and/or a different elemental composition than the p/n absorption layers of the semiconductor diode. The partial voltage sources and the tunnel diodes are monolithically integrated together, and jointly form a first stack with a top and a bottom, and the number N of partial voltage sources is greater than or equal to two.

A tunnel junction for a semiconductor device is disclosed. The tunnel junction includes a n-doped tunnel layer and a p-doped tunnel layer. The p-doped tunnel layer is constructed of aluminum gallium arsenide antimonide (AlGaAsSb). A semiconductor device including the tunnel junction with the p-doped tunnel layer constructed of AlGaAsSb is also disclosed.

A method for fabricating an upright photovoltaic cell comprises growing one or more epitaxial layers on a substrate, thereby forming a diffused active junction on the substrate and one more additional active junctions above the diffused active junction. The method further comprises selectively etching an areal region of the one or more epitaxial layers, thereby forming a mesa on the substrate and exposing a substrate-contact region parallel to the areal region at a base of the mesa. The method further comprises depositing contact material onto the substrate-contact region, to form the first contact, and concertedly onto a mesa-contact region of the mesa, to form the second contact.

A method for fabricating an upright photovoltaic cell comprises growing one or more epitaxial layers on a substrate, thereby forming a diffused active junction on the substrate and one more additional active junctions above the diffused active junction. The method further comprises selectively etching an areal region of the one or more epitaxial layers, thereby forming a mesa on the substrate and exposing a substrate-contact region parallel to the areal region at a base of the mesa. The method further comprises depositing contact material onto the substrate-contact region, to form the first contact, and concertedly onto a mesa-contact region of the mesa, to form the second contact.

Structures including crystalline material disposed in openings defined in a non-crystalline mask layer disposed over a substrate. A photovoltaic cell may be disposed above the crystalline material.

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 (0x1<1, 0<y11) layer and a first n-type (Al.sub.x2Ga.sub.1-x2).sub.y2In.sub.1-y2P (0x2<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 photoelectric conversion element of an embodiment includes a substrate, a transparent first electrode on the substrate, a second electrode, and a light absorbing layer of a homo-junction type interposed between the first electrode and the second electrode. The light absorbing layer includes a p-type region on the second electrode side and an n-type region on the first electrode side. The n-type region has an n-type dopant. The photoelectric conversion element has a boundary surface between the light absorbing layer on the n-type region side and the first electrode.

In one aspect, optoelectronic devices are described herein. In some implementations, an optoelectronic device comprises a photovoltaic cell. The photovoltaic cell comprises a space-charge region, a quasi-neutral region, and a low bandgap absorber region (LBAR) layer or an improved transport (IT) layer at least partially positioned in the quasi-neutral region of the cell.

A method of fabricating a four-junction solar cell includes: forming a first epitaxial structure comprising first and second subcells and a cover layer over a first substrate through a forward epitaxial growth, and forming a second epitaxial structure comprising third and fourth subcells over the second substrate; forming a groove and a metal bonding layer; forming a groove on the cover layer surface of the first epitaxial structure and the substrate back surface of the second epitaxial structure, and depositing a metal bonding layer in the groove; and bonding the first epitaxial structure and the second epitaxial structure; bonding the cover layer surface of the first epitaxial structure and the substrate back surface of the second epitaxial structure, ensuring that the metal bonding layers are aligned to each other to realize dual bonding between the metal bonding layers and between the semiconductors through high temperature and high pressure treatment.

A photoelectric conversion device including a transparent substrate, a first electrode, at least a photoelectric conversion layer and a second electrode is provided. The first electrode is located on the transparent substrate. The transparent substrate means that at least some parts of the substrate area are transparent. At least a photoelectric conversion layer is located on the first electrode, wherein the optical light transmittance of the photoelectric conversion layer in at least a portion of the visible spectrum is higher than 20%. The second electrode is located on the photoelectric conversion layer.