Multijunction solar cells

Patent metadata

Field	Value
Publication number	US-12249668-B2
Application number	US-202318378023-A
Country	US
Kind code	B2
Filing date	Oct 9, 2023
Priority date	Jan 28, 2021
Publication date	Mar 11, 2025
Grant date	Mar 11, 2025

Abstract

A multijunction solar cell including an upper first solar subcell having a first band gap and positioned for receiving an incoming light beam; and a second solar subcell disposed below and adjacent to and lattice matched with said upper first solar subcell, and having a second band gap smaller than said first band gap; wherein at least one of the solar subcells has a graded band gap throughout the thickness of at least a portion of its emitter layer and base layer.

First claim

The invention claimed is:

1. A multijunction solar cell comprising:
a first solar subcell, having an emitter layer and a base layer which form a photoelectric junction;
a second solar subcell disposed below and adjacent to the first solar subcell, having an emitter layer and a base layer which form a photoelectric junction; and
a third solar subcell disposed below the second solar subcell, having an emitter layer and a base layer which form a photoelectric junction;
wherein the base layer and the emitter layer of at least a particular one of the first solar subcell, the second solar subcell, and the third solar subcell has a graded band gap throughout at least a portion of a thickness of the emitter layer in a first region in the emitter layer adjacent to the photoelectric junction, and throughout at least a portion of a thickness of the base layer in a second region in the base layer spaced apart from the first region and adjacent to the photoelectric junction, with the band gap in the first region and the band gap in the second region being in the range of 20 to 300 meV greater than the band gap away from the photoelectric junction in the emitter layer and the base layer in the at least a particular one of the first solar subcell, the second solar subcell and the third solar subcell, and
wherein the thickness of the first region is less than the thickness of the second region.

2. A solar cell as defined in claim 1 , wherein the band gap in the emitter layer in the first region in the at least a particular one of the first solar subcell, the second solar subcell and the third solar subcell increases to a first level, and then decreases to a second level in the base layer in the particular one subcell that is greater in band gap than the first level.

3. A solar cell as defined in claim 1 , further comprising a third region in the emitter layer in the particular one of the first solar subcell, the second solar subcell and the third solar subcell that lies directly adjacent to and spaced apart from the first region, wherein the band gap in the third region is constant.

4. A solar cell as defined in claim 2 , further comprising a fourth region in the base layer in the particular one of the first solar subcell, the second solar subcell and the third solar subcell that lies directly adjacent to and spaced apart from the second region, wherein the band gap in the fourth region is constant.

5. A solar cell as defined in claim 3 , wherein the first level of the band gap is substantially located at the photoelectric junction of the particular one of the first solar subcell, the second solar subcell and the third solar subcell.

6. A solar cell as defined in claim 2 , wherein the second level of the band gap is substantially located in a depletion region in the base layer of the particularly one of the first solar subcell, the second solar subcell or the third solar subcell.

7. A solar cell as defined in claim 4 , wherein the band gap in the third region of the particular one solar subcell is less than the band gap in the fourth region of the particular one subcell of the first solar subcell, the second solar subcell and the third solar subcell.

8. A solar cell as defined in claim 1 , wherein a depletion region of the particular one solar subcell is asymmetric around the photoelectric junction of the at least a particular one of the first solar subcell, the second solar subcell and the third solar subcell.

9. A solar cell as defined in claim 1 , wherein the width of the graded band gap region in the particular one solar subcell is equal to the width of a depletion region in the particular one of the first solar subcell, the second solar subcell and the third solar subcell.

10. A solar cell as defined in claim 1 , wherein the band gap of the particular one of the first solar subcell, the second solar subcell and the third solar subcell has a peak that Is centered approximately where a Fermi level of the particular one solar subcell crosses mid-band.

11. A solar cell as defined in claim 1 , wherein the first and second regions of the graded band gap of the particular one of the first solar subcell, the second solar subcell and the third solar subcell is asymmetric around the depletion region of the particular one solar subcell.

12. A solar cell as defined in claim 1 , wherein the first and second region of the graded band gap of the particular one of the first solar subcell, the second solar subcell and the third solar subcell is non-symmetric around the photoelectric junction.

13. A solar cell as defined in claim 1 , wherein the first solar subcell is composed of indium gallium aluminum phosphide and has a first band gap in the range of 2.0 to 2.2 eV;
the emitter layer of the second solar subcell is composed of indium gallium phosphide or aluminum indium gallium arsenide, and the base layer of the second solar subcell is composed of aluminum indium gallium arsenide, and has a second band gap in the range of approximately 1.55 to 1.8 eV and is lattice matched with the first solar subcell; and
wherein the third solar subcell is disposed adjacent to said second solar subcell and is composed of indium gallium arsenide, and has a third band gap less than the second band gap and is lattice matched with the second solar subcell.

14. A solar cell as defined in claim 1 , wherein the solar cell is configured for optimum operation in (i) a LEO earth orbit; (ii) a GEO earth orbit; (iii)a Mars environment; or (iv) a Jupiter environment.

15. A solar cell as defined in claim 1 , wherein the first solar subcell, the second solar subcell, and the third solar subcell each have a graded band gap throughout at least a portion of the thickness of their emitter layer and base layer.

16. A solar cell as defined in claim 1 , further comprising an intermediate graded layer disposed between the particular one of the first solar subcell, the second solar subcell, and the third solar subcell and the adjacent solar subcell disposed directly below the particular one solar subcell, wherein the intermediate layer is compositionally graded to lattice match the particular one solar subcell on one side and the adjacent solar subcell on the other side, and is composed of any of the As, P, N, Sb based III-V compound semiconductors subject to the constraints of having the in-plane lattice parameter greater than or equal to that of the particular one solar subcell and less than or equal to that of the adjacent solar subcell, and having a band gap greater than that of the particular one solar subcell.

17. A solar cell as defined in claim 1 , further comprising a fourth or bottom solar subcell disposed below the third solar subcell, and
an intermediate graded layer disposed between the third solar subcell and the fourth or bottom solar subcell, wherein the intermediate layer is compositionally step-graded with between one and four steps to lattice match the third solar subcell on one side and the fourth or bottom solar subcell on the other side, and composed of InGaAs or (In x Ga 1-x ) y Al 1-y As with 0<x<1, 0<y<1, and x and y selected such that the band gap remains at a constant value in the range of 1.15 to 1.41 eV, or 1.2 to 1.35 eV, or 1.25 to 1.30 eV throughout its thickness.

18. A solar cell as defined in claim 11 , further comprising;
a distributed Bragg reflector (DBR) layer disposed adjacent to and beneath the third solar subcell and arranged so that light can enter and pass through the third solar subcell and at least a portion of which can be reflected back into the third solar subcell by the DBR layer, w

Assignees

• Solaero Tech Corp

Inventors

• Hart John
• Derkacs Daniel
• Bittner Zachary
• Espenlaub Andrew

Classifications

• H10F71/127

  The active layers comprising only Group III-V materials, e.g. GaAs or InP · CPC title

• H10F10/163

  comprising only Group III-V materials, e.g. GaAs/AlGaAs or InP/GaInAs photovoltaic cells · CPC title

• H10F10/13

  Photovoltaic cells having absorbing layers comprising graded bandgaps · CPC title

• C12P19/56

  having an oxygen atom of the saccharide radical directly bound to a condensed ring system having three or more carbocyclic rings, e.g. daunomycin, adriamycin · CPC title

• H10F10/161 Primary

  comprising multiple PN heterojunctions, e.g. tandem cells · CPC title