Space vehicles including multijunction metamorphic solar cells

Patent metadata

Field	Value
Publication number	US-12249667-B2
Application number	US-202117180210-A
Country	US
Kind code	B2
Filing date	Feb 19, 2021
Priority date	Aug 18, 2017
Publication date	Mar 11, 2025
Grant date	Mar 11, 2025

Abstract

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 5×10 14 electron fluence per square centimeter (“e/cm 2 ”) over a five year EOL, or (ii) a geosynchronous earth orbit (GEO) satellite that typically experiences radiation in the range of 5×10 14 e/cm 2 to 1×10 15 e/cm 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).

First claim

The invention claimed is:

1. A plurality of space vehicles, each space vehicle comprising:
a housing having a first side and 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,
wherein the multijunction solar cell on the first and second rectangular sheet comprises:
a germanium growth substrate;
a first or bottom solar subcell disposed over or in the germanium growth substrate;
a graded interlayer disposed over the germanium growth substrate,
a first middle solar subcell disposed over the graded interlayer and lattice mismatched with respect to the growth germanium substrate having a band gap in the range of 1.06 to 1.41 eV;
a second middle solar subcell disposed over the first middle solar subcell and having a band gap in the range of approximately 1.35 to 1.66 eV;
a third middle solar subcell disposed over and lattice mismatched with respect to the growth substrate and having a band gap in the range of 1.665 to 1.95 eV; and
an upper solar subcell disposed over the third middle solar subcell and having a band gap in the range of 1.95 to 2.20 eV;
wherein the graded interlayer is compositionally graded to lattice match the growth substrate on one side and the first middle solar subcell on the other side, and is composed of the As, P, N, Sb based III-V compound semiconductors subject to the constraints of having the in-plane lattice parameter throughout its thickness being greater than or equal to that of the growth substrate.

2. A plurality of space vehicles as defined in claim 1 , wherein the plurality of space vehicles are substantially identical and are disposed in one or more LEO orbits forming a satellite constellation, and
further comprising a network of ground stations on the earth providing a communications networks for users on the earth in communication with the satellite constellation.

3. A plurality of space vehicles as defined in claim 1 , wherein:
the upper solar subcell is composed of indium gallium aluminum phosphide;
the first middle solar subcell is composed of (aluminum) indium gallium phosphide;
the second middle solar subcell includes an emitter layer composed of indium gallium phosphide or aluminum indium gallium arsenide, and a base layer composed of aluminum indium gallium arsenide;
the third middle solar subcell is composed of (aluminum) indium gallium phosphide;
the first or bottom solar subcell disposed in the germanium growth substrate; and
the graded interlayer is composed of (In x Ga 1-x ) y Al 1-y As with 0<x<1, 0<y<1.

4. A plurality of space vehicles as defined in claim 1 , wherein a tunnel diode is deposited over the growth substrate, with the graded interlayer grown over the tunnel diode.

5. A plurality of space vehicles as defined in claim 1 , wherein the aluminum content in the upper solar subcell is in excess of 30% by mole fraction.

6. A plurality of space vehicles as defined in claim 1 , further comprising:
a distributed Bragg reflector (DBR) structure disposed between the first or bottom solar subcell and the first middle solar subcell and composed of a plurality of alternating layers of lattice mismatched materials with discontinuities in their respective indices of refraction and arranged so that light can enter and pass through the first middle solar subcell and at least a first portion of which light having a first spectral width wavelength range including the band gap of the first middle solar subcell can be reflected back into the first middle solar subcell by the DBR structure, and a second portion of which light in a second spectral width wavelength range corresponding to longer wavelengths than the first spectral width wavelength range can be transmitted through the DBR structure to the first or bottom solar subcell disposed beneath the DBR structure, and wherein the difference in refractive indices between the alternating layers in the DBR structure is maximized in order to minimize the number of periods required to achieve a given reflectivity, and the thickness and refractive index of each period of the DBR structure determines the stop, its limiting wavelength, and wherein the DBR structure includes a first DBR sublayer composed of a plurality of n-type or p-type Al x (In)Ga 1-x As layers, and a second DBR sublayer disposed over the first DBR sublayer and composed of a plurality of n-type or p-type Al y (In)Ga 1-y As layers, where 0<x<1, 0<y<1, and y is greater than x and (In) represents an amount of indium so that the DBR layers are lattice matched to the first or bottom solar subcell.

7. A plurality of space vehicles as defined in claim 1 , wherein one or more of the solar subcells have a base region having a gradation in doping that increases exponentially from a value in the range of 1×10 15 to 1×10 18 free carriers per cubic centimeter adjacent the p-n junction to a value in the range of 1×10 16 to 4×10 18 free carriers per cubic centimeter adjacent to the adjoining layer at the rear of the base layer, and an emitter layer having a gradation in doping that decreases from a value in the range of approximately 5×10 18 to 1×10 17 free carriers per cubic centimeter in the region immediately adjacent the adjoining layer to a value in the range of 5×10 15 to 1×10 18 free carriers per cubic centimeter in the region adjacent to the p-n junction.

8. A plurality of space vehicles as defined in claim 1 , further comprising an intermediate transition layer disposed between the upper solar subcell and the third middle solar subcell, and wherein the band gap of the upper solar subcell is greater than 2.0 eV.

9. A plurality of space vehicles as defined in claim 1 , wherein the second middle solar subcell includes a plurality of quantum well layers that are “strain balanced” by incorporating alternating lower band gap (or larger lattice constant) compressively strained InGaAs and higher band gap (or smaller lattice constant) tensionally strained GaAsP, GaAs, InGaAs, or GaAsN layers so that the larger/smaller atomic lattices/layers of epitaxy balance the strain to keep the quantum well layers lattice matched.

10. A plurality of space vehicles as defined in claim 1 , wherein the selection of the composition of the solar subcells and their band gap maximizes the efficiency of the solar cell at a predetermined low intensity (less than 0.1 suns) and predeterminate time after the initial deployment in space of the space vehicle (after the “beginning-of-life (BOL)”), such predetermined time being referred to as the “end-of-life (EOL)” time, and being at least one year.

11. A plurality of space vehicles as defined in claim 1 , wherein the band gap of the first middle solar subcell is in the range of 1.064 to 1.2 eV;
the band gap of the second middle solar subcell has a band gap in the range of approximately 1.35 to 1.48 eV;
the band gap of the third middle solar subcell has a band gap in the range of 1.665 to 1.78 eV; and the band gap of the upper solar subcell is 2.1 eV.

12. A plurality of space vehicles as defined in claim 1 , wherein the upper solar subcell has a band gap of approximately 2.05 to 2.10 eV; and the first middle solar subcell has a band gap in the range of 1.15 to 1.41 eV.

13. A plurality of space vehicles as defined in claim 10 , wherein the solar cell efficiency at the BOL is the lowest value of efficiency in the time period from

Assignees

• Solaero Tech Corp

Inventors

• Derkacs Daniel

Classifications

• B64G1/222

  for deploying structures between a stowed and deployed state · CPC title

• H10F71/1276

  comprising growth substrates not made of Group III-V materials · CPC title

• H10F71/1272

  comprising at least three elements, e.g. GaAlAs or InGaAsP · CPC title

• H10F71/1212

  consisting of germanium · CPC title

• H10F10/164

  comprising heterojunctions with Group IV materials, e.g. ITO/Si or GaAs/SiGe photovoltaic cells · CPC title