Systems, methods, and apparatus for light collection and conversion to electricity are disclosed herein. The disclosed method involves receiving, by at least one concentrating element (e.g., a lens), light from at least one light source, where the light comprises direct light and diffuse light. The method further involves focusing, by at least one concentrating element, the direct light onto at least one concentrator photovoltaic cell. Also, the method involves passing, by at least one concentrating element, the diffuse light onto at least one solar cell of an array of solar cells arranged on a flat plate, where at least one concentrator photovoltaic cell is bonded on top of at least one of the solar cells in the array. In addition, the method involves collecting, by at least one concentrator photovoltaic cell, the direct light. Further, the method involves collecting, by at least one solar cell, the diffuse light.

A low bandgap absorber region (LBAR) used in a laser power converter (LPC). The laser power converter is comprised of one or more subcells on a substrate, wherein at least one of the subcells has an emitter and base, with the low bandgap absorber region coupled between the emitter and base. The emitter and base are comprised of a material with a bandgap higher than a wavelength of incident laser light, and the low bandgap absorber region is comprised of a material with a bandgap lower than the emitter and base. The emitter and base are transparent to the incident laser light, and the low bandgap absorber region absorbs the incident laser light and generates a current in response thereto, such that the current is controlled by the material and thickness of the low bandgap absorber region. The low bandgap absorber region is configured to produce a current balanced to the subcells connected in series.

The present disclosure provides a multijunction solar cell that includes: a first sequence of layers of semiconductor material forming a first set of one or more solar subcells; a graded interlayer adjacent to said first sequence of layers; a second sequence of layers of semiconductor material forming a second set of one or more solar subcells; and a high band gap contact layer adjacent said second sequence of layers, wherein the high band gap contact layer is composed of p++ type InGaAlAs or InGaAs.

The disclosure provides for a direct wafer bonding method including providing a bonding layer upon a first and second wafer, and directly bonding the first and second wafers together under heat and pressure. The method may be used for directly bonding an GaAs-based, InP-based, GaP-based, GaSb-based, or Ga(In)N-based device to a GaAs device by introducing a highly doped (Al)(Ga)InP(As)(Sb) layer between the devices. The bonding layer material forms a bond having high bond strength, low electrical resistance, and high optical transmittance.

A method for producing an optical device includes: forming an n-type layer over a substrate by a MOCVD method; forming a first active layer over the n-type layer by a MOCVD method; forming an intermediate layer over the first active layer by a MOCVD method; forming a second active layer having a band gap energy different from the band gap energy of the first active layer over the intermediate layer by a MOCVD method; forming a first p-type layer over the second active layer by a MOCVD method; forming a groove having a depth reaching the intermediate layer from a side of the first p-type layer; forming an electron blocking layer by sputtering over the intermediate layer exposed at a bottom surface of the groove; forming a semiconductor layer over the electron blocking layer by sputtering; and forming a second p-type layer as defined herein.

A highly doped layer for interconnecting tunnel junctions in multijunction solar cells is presented. The highly doped layer is a delta-doped layer in one or both layers of a tunnel diode junction used to connect two or more p-on-n or n-on-p solar cells in a multijunction solar cell. A delta-doped layer is made by interrupting the epitaxial growth of one of the layers of the tunnel diode, depositing a delta dopant at a concentration substantially greater than the concentration used in growing the layer of the tunnel diode, and then continuing to epitaxially grow the remaining tunnel diode.

A low bandgap absorber region (LBAR) used in a laser power converter (LPC). The laser power converter is comprised of one or more subcells on a substrate, wherein at least one of the subcells has an emitter and base, with the low bandgap absorber region coupled between the emitter and base. The emitter and base are comprised of a material with a bandgap higher than a wavelength of incident laser light, and the low bandgap absorber region is comprised of a material with a bandgap lower than the emitter and base. The emitter and base are transparent to the incident laser light, and the low bandgap absorber region absorbs the incident laser light and generates a current in response thereto, such that the current is controlled by the material and thickness of the low bandgap absorber region. The low bandgap absorber region is configured to produce a current balanced to the subcells connected in series.

A multijunction solar cell including an upper first solar subcell having an emitter and base layers forming a photoelectric junction; a second solar subcell disposed under and adjacent to the upper first solar subcell, and having an emitter and base layers forming a photoelectric junction; and a third solar subcell disposed under and adjacent to the second solar subcell and having an emitter and base layers forming a photoelectric junction; wherein at least one of the base and emitter layers of at least a particular solar subcell from among the upper first solar subcell, the second solar subcell, and the third solar subcell has a graded band gap throughout at least a portion of thickness of its active layer adjacent to the photoelectric junction and being in a range of 20 to 300 MeV greater than a band gap in the active layer in both the emitter layer and the base layer spaced away from the photoelectric junction.

A multijunction solar cell including an upper first solar subcell having an emitter and base layers forming a photoelectric junction; a second solar subcell disposed under and adjacent to the upper first solar subcell, and having an emitter and base layers forming a photoelectric junction; and a third solar subcell disposed under and adjacent to the second solar subcell and having an emitter and base layers forming a photoelectric junction; wherein at least one of the base and emitter layers of at least a particular solar subcell from among the upper first solar subcell, the second solar subcell, and the third solar subcell has a graded band gap throughout at least a portion of thickness of its active layer adjacent to the photoelectric junction and being in a range of 20 to 300 MeV greater than a band gap in the active layer in both the emitter layer and the base layer spaced away from the photoelectric junction.

A stacked monolithic upright metamorphic multijunction solar cell, comprising at least one first subcell having a first band gap, a first lattice constant and being made up of germanium by more than 50%, a second subcell, which is disposed above the first subcell and has a second band gap and a second lattice constant, a metamorphic buffer disposed between the first subcell and the second subcell, including a sequence of at least three layers having lattice constants which increase from layer to layer in the direction of the second subcell, and a first tunnel diode, which is situated between the metamorphic buffer and the second subcell and which has an n.sup.+ layer and a p.sup.+ layer, the second band gap being larger than the first band gap, the n.sup.+ layer of the first tunnel diode comprising InAlP, the p.sup.+ layer of the first tunnel diode comprising an As-containing III-V material.