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 plurality of space vehicles forming a satellite constellation, each space vehicle comprising a housing having a first side and an opposite side, and an axis; a first elongated, rectangular sheet including an array of transducer devices including multijunction solar cells mounted on, and extending from a surface of the first side of the housing, and a second elongated rectangular sheet including an array of transducer devices including multijunction solar cells mounted on and extending from a surface of the second side of the housing in a direction opposite to that of the first elongated rectangular sheet, wherein the selection of the composition of the subcells and their band gap of the multijunction solar cells maximizes the efficiency of the solar cell at the end-of-life EOL in the application of one of (i) a low earth orbit (LEO) satellite that typically experiences radiation equivalent to 510.sup.14 electron fluence per square centimeter (e/cm.sup.2) over a five year EOL, or (ii) a geosynchronous earth orbit (GEO) satellite that typically experiences radiation in the range of 510.sup.14 e/cm.sup.2 to 110.sup.15 e/cm.sup.2 over a fifteen year EOL, with the efficiency of the multijunction solar cells being less at the beginning-of-life (BOL) than the end-of-life (EOL).

A method of fabricating four junction solar cell wherein the selection of the composition of the subcells and their band gaps maximizes the efficiency at high temperature (in the range of 50 to 100 degrees Centigrade) in deployment in space at a specific predetermined time after initial deployment (referred to as the beginning of life or BOL), such predetermined time being referred to as the end-of-life (EOL), and being at least five years after the BOL, such selection being designed not to maximize the efficiency at BOL but to increase the solar cell efficiency at the EOL while disregarding the solar cell efficiency achieved at the BOL, such that the solar cell efficiency designed at the BOL is less than the solar cell efficiency at the BOL that would be achieved if the selection were designed to maximize the solar cell efficiency at the BOL.

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.

In one aspect, semiconductor structures are described herein. A semiconductor structure, in some implementations, comprises a first semiconductor layer having a first bandgap and a first lattice constant and a second semiconductor layer having a second bandgap and a second lattice constant. The second lattice constant is lower than the first lattice constant. Additionally, a transparent metamorphic buffer layer is disposed between the first semiconductor layer and the second semiconductor layer. The buffer layer has a constant or substantially constant bandgap and a varying lattice constant. The varying lattice constant is matched to the first lattice constant adjacent the first semiconductor layer and matched to the second lattice constant adjacent the second semiconductor layer. The buffer layer comprises a first portion comprising Al.sub.yGa.sub.zIn.sub.(1-y-z)As and a second portion comprising Ga.sub.xIn.sub.(1-x)P. The first portion is adjacent the first semiconductor layer and the second portion is adjacent the second semiconductor layer.

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.

Solar cell structures comprising a plurality of solar cells, wherein each solar cell is separated from adjacent solar cell via a tunnel junction and/or a resonant tunneling structure (RTS), are described. Solar cells are implemented on Ge, Si, GaN, sapphire, and glass substrates. Each of the plurality of solar cells is at least partially constructed from a cell material which harnesses photons having energies in a predetermined energy range. In one embodiment each solar cell comprises of at least two sub-cells. It also describes a nano-patterned region/layer to implement high efficiency tandem/multi-junction solar cells that reduces dislocation density due to mismatch in lattice constants in the case of single crystalline and/or polycrystalline solar cells. Finally, solar structure could be used as light-emitting diodes when biased in forward biasing mode. The mode of operation could be determined by a programmed microprocessor.